The plasma amino acid concentrations were investigated before and after 3 and 30 months of human recombinant growth hormone treatment in 7 children with chronic renal failure. The concentrations of amino acids in plasma showed characteristic changes (pretreatment vs. after 3 and 30 months of treatment): Lys 113 +/- 33 vs. 162 +/- 27 and 109 +/- 38 mumol/l, Met 21 +/- 8 vs. 31 +/- 4 and 16 +/- 5, Thr 105 +/- 23 vs. 148 +/- 60 and 118 +/- 30, Ala 455 +/- 109 vs. 536 +/- 93 and 314 +/- 60, Gln 298 +/- 66 vs. 277 +/- 52 and 544 +/- 65, Glu 168 +/- 46 vs. 209 +/- 57 and 96 +/- 24, Gly 345 +/- 137 vs. 479 +/- 169 and 342 +/- 95, Pro 378 +/- 148 vs. 422 +/- 28 and 527 +/- 229, OH-Pro 33 +/- 17 vs. 105 +/- 23 and 97 +/- 35, Se 133 +/- 39 vs. 178 +/- 55 and 131 +/- 12 mumol/l. Long-term treatment with human recombinant growth hormone normalized plasma alanine, glutamine, and glutamic acid levels, increased the OH-Pro concentration, and did not alter the amino acid ratios of Gly/Val, Phe/Tyr, Ser/Gly, and Asn/Asp, but the Gln/Glu ratio approached the normal value.