The hypophyseal human growth hormone (hGH), a Raben type laboratory preparation, was re-evaluated as regards its innocuity for therapeutic use. Besides the usual control tests recommended by the Romanian Pharmacopoeia, the contamination of the hGH for clinical use with acute and slow viruses, was investigated taking into account the withdrawal of this hormone in many developed countries. The contamination was absent both with acute viruses as resulted from hemadsorption on cell cultures and counterimmunoelectrophoresis, and with slow viruses as observed from a two year-follow up of guinea pigs injected intracerebrally with the hGH preparation. Further, the content of the growth hormone itself as well as the contamination degree with other pituitary hormones was examined. The hGH-RIA content was 2.23 +/- 0.13 IU/mg (means +/- SEM), range: 1.38-2.80 IU/mg (1st International Standard hGH 80/505-1982). The prolactin contamination assessed by RIA was 187.34 +/- 37.66 ng/mg hGH, range: 28.44-385.20 ng (International Standard WHO: 80/541). The LH and FSH contamination as quantified by the Isocommerz (DDR) RIA kits was with two orders of magnitude lower than 10 IU-LH/IU-hGH, the upper LH contamination limit considered as acceptable. Moreover, the proportion of the large molecular forms in the lyophilized hGH preparation was investigated by polyacrylamide gel electrophoresis. Corroborating the data obtained by these control tests with our previous experience on 149 pituitary dwarfs treated with this hGH preparation during the interval 1964-1984, resulted minor risks of some dangerous side effects of hGH administration in children with growth hormone deficiency by possible contamination with pathogenic agents or with other disturbing hormones.