We studied the effect of natural and synthetic androgens on children’s erythropoietic precursor cells in culture. Cultures of normal marrow were carried out according to a miniaturized methylcellulose method in the presence of erythropoietin. We then evaluated the effects of testosterone, nortestosterone, fluoxymesterone and etiocholanolone (10<sup>-9</sup>–10<sup>-6</sup> M) on erythroid colony-forming units (CFU-E) and burst-forming units (BFU-E). Androgen-induced growth of erythroid progenitors was quantified by directly scoring colonies and by a biochemical determination of the uroporphyrinogen I synthase activity (UROS). We observed a significant increase (p ≤ 0.05) in the number of CFU-E and BFU-E and in the UROS activity of derived colonies in the presence of androgens (10<sup>-8</sup> or 10<sup>-7</sup> M). This microculture assay could be useful not only to study the effect of androgens on erythroid progenitor cells in culture, but also to predict the best androgenic treatment of anemia in children and adults.