The common frequency of the nontasting gene for phenylthiocarbamate (about 28%) has been found both in Indian adults and in Indian children aged between 6 and 11 years. However, a much lower frequency (less than 11%) was obtained when both Turkish adults and Turkish children aged between 6 and 11 years were tested. On the other hand. English children under the age of 7 years possessed a higher frequency (up to 60%). English children aged 9 years or older had a frquency comparable with that of English adults (about 28%). It was found that between the ages of 7 and 9 many English nontaster children became tasters, which accounts for the observed change in frequency. The reasons for these variations are being investigated.