The influence of biosynthetic human growth hormone on biomechanical properties (strain at maximum load, maximum load, relative failure energy, maximum stiffness) and collagen content of intact rat skin was measured after injection of biosynthetic human growth hormone for 90 days at doses of 0.16, 1.10 and 8.33 mg.kg-1.day-1. The mechanical test showed that strain at maximum load, maximum load and relative failure energy increased with increasing doses of biosynthetic hGH. In the group receiving 8.33 mg.kg-1.day-1, skin collagen content per surface area and skin collagen concentration in per cent of dry weight were increased, whereas the fat concentration in per cent of dry weight was decreased. Also when correcting the mechanical data for cross-sectional area, a positive correlation between dose and relative failure energy was found. When dividing the mechanical data by collagen content per surface area of the skin, the maximum stress and relative failure energy reached the highest value at a dose of 1.10 mg.kg-1.day-1. The study shows that biosynthetic hGH can induce an increase in collagen content and mechanical strength of intact rat skin which is dependent on the dose of biosynthetic hGH, and that the increase in mechanical strength cannot be explained only by an increased collagen content.