A field experiment was carried out in two seasons (2007 and 2008) at the Teaching and Research Farm of the Department of Crop Science, University of Nigeria, Nsukka. The experiment evaluated the growth and yield performances of three cultivars of cassava (Manihot esculenta Crantz) and four pigeonpea (Cajanus Cajan (L) Millsp) genotypes in intercropping systems. The treatments comprised three tropical manihot cultivars (TMS 60447, TMS30572 and NR8082), and four pigeonpea genotypes comprising three improved International Crop Research Institute for the Semi-Arid Tropics (ICRISAT), genotypes of two short-duration (ICPL 87 and ICPL 161), one medium-duration (ICPL 7120) and large seeded long-duration local landrace (NSUKKA LOCAL). The treatments were laid out in randomized complete block design (RCBD), with three replications. The sole pigeonpea was sown 40,000 stands/ha while the sole for cassava was 10,000. Mixture was in additive series ie 40,000 for pigeonpea + 10,000 for cassava giving pigeonpea/cassava of 50,000 plants per hectare. The data collected were subjected to the analysis of variance technique for randomized complete block design using Genstat (3) discovery package of statistical analysis. Treatment means were separated for significant differences using the least significant differences (LSD) procedure at 5% level of probability. Results showed that intercropping significantly (p< 0.05) shortened days to 50% pigeonpea emergence, depressed cassava plant height and increased pigeonpea plant height. The number of leaves per plant in pigeonpea was depressed while that of cassava was not affected by the intercropping. The number of branches, length (cm) of leaf stalk, leaf area (cm2) in cassava were significantly (p< 0.05) depressed by intercropping. Pigeonpea stem girth (cm) and cassava plant height (cm) were significantly (p<0.05) reduced while pigeonpea plant height (cm) and cassava stem girth (cm) were statistically (p<0.05) increased by intercropping. The number of cassava branches per plant was significantly (p<0.05) reduced expect with cassava cultivar TMS 30572 in mixture with four pigeonpea genotypes. The number of primary branches and number of leaves per plant in pigeonpea at harvest were significantly (p<0.05) decreased by intercropping system. The number of leaves, leaf area (cm2) and leaf area index in cassava at harvest were significantly (p<0.05) decreased by the mixture except with cassava leaf area and leaf area index of TMS 60447 + ICPL 7120. Days of pigeonpea 50% flowering and 50% maturity were all significantly (p<0.05) increased by the intercropping system. The pigeonpea inflorescence length (cm) and number of pods/plant were significantly (p<0.05) depressed except ICPL 161 and ICPL 7120 in mixture with three cassava cultivars. The number of insects per plant of both the short-and medium-duration pigeonpea genotypes at flowering and podding stage were significantly (p<0.05) decreased by the intercropping system except the long-duration (NSUKKA LOCAL) pigeonpea genotype. Nevertheless, the intercropping system significantly (p<0.05) increased the number of pigeonpea numbr of damaged pods/plant and decreased number of damaged seeds/plant. The pod length (cm) for short-and medium-duration pigeonpea genotypes were significantly (p<0.05) depressed by the intercropping system except the long duration pigeonpea. The pigeonpea number of seeds/pod and number of seeds/plant were significantly (p<0.05) increased except ICPL 161 in intercrop with three cassava cultivars for seed/pod and long-duration genotype for number of seeds/plant. The number of tubers/plant, average tuber weight (g), fresh tuber weight/plant (g) and tuber weight tons/ha were significantly (p<0.05) depressed by the cropping system. The seed yield/plant (g) and seed yield kg/ha of short-and medium-duration pigeonpea genotypes were all significantly (p<0.05) increased by the mixture except long-duration pigeonpea (NSUKKA LOCAL). The average 1000 seed weight (g) was significantly (p<0.05) depressed and the threshing percentage was significantly enhanced by the intercropping system. In ratooning pigeonpea crop survived significantly (p<0.05) higher in long-duration pigeonpea genotype compared with short-and medium-duration ICRISAT genotypes. The intercropping efficiencies of the pigeonpea/cassava mixture were analyzed using the land equivalent ratio (LER) analysis and the actual economic or monetary values were also assessed. Land equivalent ration (LER) values greater than one (>1.0) were obtained in all pigeonpea/cassava mixtures except cassava cultivar NR8082 mixed with long-duration pigeonpea genotype, NSUKKA LOCAL, (NR8082 + NSUKKA LOCAL). Sole cassava cultivars gave greater monetary values than sole pigeonpea genotypes but pigeonpea genotypes in mixture gave greater monetary values than their cassava counterpart in the mixture. The pigeonpea ratoon crops were assessed for their survival and grain yield in 2009. Ratooning in pigeonpea was 61.5%. The long-duration pigeonpea genotypes ratooned more than the short-and medium-duration ICRISAT pigeonpea genotypes and intercropping significantly (p<0.05) depressed ratooning ability of pigeonpea genotypes. The mean ratoon crop values in the following yield parameters were 94.2% pod length (cm), 79.5% number of seeds/pod, 81% number of pods/plant and 86.7% number of seeds/plant compared with the situation for the main crop. The depressant effects of cassava in mixture on pigeonpea were grain yield (29.1%), pod length (cm) (5.8%), number of seeds/pod (20.5%). NSUKKA LOCALhad lower insect damage of the pod and seed compared to ICRISAT pigeonpea gentoypes (ICPL87, ICPL 161 and ICPL 7120) in previously intercropped pigeonpea ratoon crops. NSUKKA LOCAL had more grain yield/plant (g) and more kg/ha in the main intercropped pigeonpea than with ratoon crops of ICRISAT pigeonpea genotypes.