344 couples with infertility unrelated to female organic pelvic disease underwent Direct Intraperitoneal Insemination (DIPI) for a total of a 429 DIPI cycles. Pregnancy per couple was 16.5% and per DIPI cycle 13.2%. DIPI was particularly effective in cases of infertility due to cervical mucus insufficiency and unexplained infertility with results respectively of 33.7% and 30.4% per couple and 30.7% and 28.7% per DIPI cycle. On the contrary, the results regarding male subfertility were 12.5% per couple and 10.5% per DIPI cycle. A significant difference was found (X2 A = 16.48, p less than 0.001) between these results and those of the group composed of cases of cervical mucus insufficiency and unexplained infertility. In cases of antisperm iso- and autoimmunization the results were on the whole poor, and were in any case influenced by corticosteroid pretreatment. The Pellet Swim-up Test (PST) proved to be a good prognostic sign for success of DIPI, since a significant difference was found between the PST group greater than or equal to 1.5 X 10(6)/ml (pregnancy per couple was 19.7% and per DIPI cycle 17.2%) and PST group less than 1.5 X 10(6)/ml (pregnancy per couple was 6.8% and per DIPI cycle was 4.5%) (X2 = 11.4. P less than 0.001).