The ability to taste P.T.C. was observed among 128 indians not closely related (not parents and children, nor brothers), belonging to the Tucano group of the region of Uauptss, on the upper Negro River, State of Amazonas, Brazil, there being fifty-five males and seventy-three females in the sample. The technique used was that of Harris and Kalmus.

In the whole group, the results show a proportion of 6.24% of non-tasters, with a clear difference in the distribution of the character in the two sexes: 12-6 % of non-tasters among males, and 1–4 % among females, which gives a x2 of 6.64, with P =0.01.