Plasma taurine levels and urinary taurine excretion were measured in 12 strict vegetarian (vegan) males who had maintained a vegan diet for 53 +/- 26 mo (SD) and in 14 male nonvegetarian control subjects. Plasma taurine levels differed (45 +/- 7 vs 58 +/- 16 mumol/L, respectively). Urinary taurine excretion was lower (266 +/- 279 vs 903 +/- 580 mumol/d), urinary N pi-methylhistidine was barely detectable, and urinary N tau-methylhistidine was significantly reduced (296 +/- 87 vs 427 +/- 19 mumol/d) in the vegans. Analysis of 3-d dietary diaries kept by the vegans indicated marginal to adequate intake of protein, carbohydrate, vitamin B-6, methionine, and cystine; inadequate intake of zinc; and negligible intake of taurine. Prolonged absence of dietary taurine intake causes decreased plasma taurine and severely restricted urinary taurine output.