The objective of this study was to determine the variability in the content of proteins and lectins in a population of Canavalia ensiformis (L.) DC. High levels of lectins were detected using horse erythrocyte hemagglutination, of which 77-98 % corresponded to Concanavalin A (Con A) as determined by hemagglutination inhibition with a-methylmannoside, an specific Con A inhibitor. In the crude extract from seeds of 102 plants the protein content was 169 ± 35 mg/g of meal compared to 140 ± 19 (Agg U)mg/g of meal in the S1 seeds (non significant). The 102 original seeds exhibited 15 060 ± 2681 agglutination units per gram of meal whereas S1 seeds showed 13 191 ± 2298 Agg U/g of meal. Heritability in the broad sense was 9.26 % for proteins and 1.38 % for agglutination. Low negative, but significant, correlation coefficients were detected between protein content and agglutination units and the number of seeds per plant. Between protein content and agglutination units and number of seeds per pod, the correlations were insignificant. Between agglutination units and number of pods per plant, the correlations were insignificant and significant between protein content and number of pods per plant. The seeds extracts had mitogenic activity for human lymphocytes, as determined by 3H-thymidine incorporation. This activity corresponded to 42-98 % to Con A when compared with commercial Con A. The presence of carbohydrates negatively correlated with the hemagglutinating ability of the extracts.