In a study of glucosinolates, determined by quantifying their hydrolysis products, goitrin (5-vinyl-oxazolidine-2-thione), volatile isothiocyanates, and thiocyanate ion, in marketable roots of 10 cultivars of summer turnip (Brassica rapa L.) and five cultivars of rutabaga (B. napobrassica L.), one turnip cultivar, Hybrid Petite White, was found to be free of goitrin, one of the most potent of natural goitrogens. In turnips, the contents of the glucosinolate products generally increased with increasing maturity dates. In rutabagas, the mean contents of thiocyanate ion were lower in early seeded (27 May) than in late-seeded (21 June) crops.