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The ability to taste phenylthiourea (PTC) was tested among 1021 Quechua-speaking subjects from the Central Highlands and Eastern Low­lands, and 864 Mestizo subjects from the Eastern Lowlands of Peru. In addition, 1137 Quechuas and 873 Mestizos were tested for the frequency of tongue rolling and right hand/left hand clasping. Among the lowland Quechua Indians and lowland Mestizos the frequency of non-tasters equals approximately 6.8% for both groups, while for the highland group it equals 3%; it is suggested that the similarity in non-taster frequency between the lowland Quechuas and Mestizos may reflect the common environment. The frequency of tongue rolling is greater for the Mestizos (65%) than for the Quechuas (53%). The frequency of right hand clasping does not show any differences between the three populations.