The objective of the present study was to evaluate the efficacy and safety of the application of the new soluble pharmaceutical form of Rastan for subcutaneous injections at a dose of 15 IU/ml and compare its action with that of Rastan lyophilisate, 4 IU, designed to prepare solutions for subcutaneous administration. The two dosage forms are used to treat children suffering from growth hormone deficiency. The study included patients at the age from 4 to 12 years presenting with idiopathic growth hormone deficiency; they were randomized into two groups. During the first three months, the patients of both groups were treated with different pharmaceutical forms of recombinant growth hormone (rGH). The children in group 1 were given Rastan for subcutaneous injections and those in group 2 received Rastan lyophilysate for the preparation of solutions for the subcutaneous administration. Either form of GH was used at an equal daily dose of 0.033 mg/kg b.w. The patients of both groups showed marked improvement of the parameters of linear growth within the first three months. The difference in the growth rates was not significantly different between the two groups which suggests the identical effect of the two forms of rGH. During the next 9 months when the patients of both groups were treated only with the rGH for subcutaneous injections, the absolute growth response, height SDS, and the level of insulin-like growth factor 1 (IGF-1) continued to increase. It points out to the stable growth-promoting effect of Rastan for subcutaneous injections. No clinically significant abnormal changes in the results of complete blood cell count and biochemical analysis of blood were apparent during 12 months of therapy with this form of rGH. The same was true of the levels of free T4, cortisol, and prolactin in the blood. No adverse effects attributable to the therapy with rGH were documented.