Retrograde ejaculation severely compromises male fertility. The use of sympathicomimetics for the treatment of this condition has poor results, except in patients with partial retrograde ejaculation, whose semen has a higher spermatozoa concentration. The semen of two patients with partial retrograde ejaculation was collected and frozen after the injection of a sympathicomimetic (Midodrine). The frozen/thawed samples were mixed with fresh semen recently ejaculated to obtain a minimal number of motile spermatozoa, and used for intrauterine insemination (> de 1 x 106 motile spermatozoa/ml). In both cases, pregnancies that developed satisfactorily, were obtained. (Rev Méd Chile 2000; 128: 93-97)