1. p-Guanidino- and p-guanidinomethyl-phenylalanine increase the renal excretion of lysine especially and, to some extent, cystine in the phenylalanine-loaded rat. The methyl derivative is the more effective.
2. The lysinuria is dose-dependent, reversible, pronounced when the intravenous infusion of analogue exceeds 10 μmol min−1 kg−1 and does not appear to be secondary to changes in urine flow or sodium excretion.
3. A mechanism for induced basic aminoaciduria conditions is suggested.