Seven samples of seeds from the genera Mucuna and Stizolobium (Leguminosae) were collected throughout southern China. HPLC analysis revealed l-dopa concentrations ranging from 3.9 to 6.2%. The seeds of the most commercially available species, S. pruriens var. utilis, collected biweekly during the fruit period, were also assayed using the same method, and their l-dopa concentrations were found to vary between 4.2 to 10.6%. Other nitrogenous compounds, which are significant in chemotaxonomy between the two plant types or have potential influence on analysis of l-dopa in the seeds were identified as stizolamine (3,4-dihydro-5-hydroxymethyl-4-methyl-3-oxopyrazinyl-guanidine), l-3 carboxy-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, and its derivatives.