Analysis of the isothiocyanates arising from enzymatic hydrolysis of glucosinolate extracts of Tropaeolum tuberosum supports the assessment of two subspecies. Seeds, tubers, leaves and flowers of T. tuberosum subsp, tuberosum produced p-methoxybenzyl isothiocyanate. Subspecies silvestre produced benzyl-, 2-propyl- and 2 butylisothiocyanates. N,N-Di(4-methoxybenzyl)thiourea was detected in tuber extracts of subsp, tuberosum by HPLC.