Hair samples from seven sick Ghanaian children were analyzed for amino acids. Cystine was determined by a procedure of Friedman using tributylphosphine and 2-vinylpyridine to change residues of cystine (and cysteine, if present) to S-beta-(2-pyridylethyl)-L-cysteine (2-PEC). This acid-stable derivative is released by normal acid hydrolysis and is eluted as a well-resolved peak before lysine in conventional ion-exchange amino acid analysis. The average cystine content of six children suffering from kwashiorkor or marasmic kwashiorkor was found to be about 20% less than that of the one remaining child, whose protein nutrition was judged adequate. In view of conflicting evidence of the relation of hair cystine content and nutrition, we believe further definitive studies of this subject are urgent. No other substantial difference in amino acid composition was noted.