BACKGROUND Although FIVET and ICSI efficacy and efficiency are continuously increasing, intrauterine insemination (IUI) is a very used technique for many different types of sterility. It is also used in male sterility for its cost/benefit positive rate. Pregnancies frequency obtained after IUI in male factor infertility cases, with or without ovarian stimulation, shows the value of this work. METHODS We evaluated 149 insemination cycles in 34 couples with a male infertility diagnosis confirmed after at least 2 semen analysis, according to OMS criteria. All the 34 patients had at least one Fallopian tube open and some spontaneous ovulatory cycle to enter in this study. The patients without biochemical pregnancy signs after 6 intrauterine insemination cycles were induced to multiple ovulations through oral administration of 50 mg of Clomifene citrate from the 5th to the 9th cycle-day or through intramuscular administration of 75 I.U. of FSH from the 5th cycle-day. A luteal support with 200 mg of vaginal progesterone, 2 times for day, was reserved for all the patients with endometrium <8 mm or with low progesterone serum levels (<20 nmol/l). RESULTS All patients made 149 IUI cycles, with a total medium pregnancy rate for cycle of 6.0% and for patient of 26.4%. We didn't observe statistically significant differences related to spermatozoa total number for ml in native sperm, in terms of pregnancy rate in men with 100-150 millions of spermatozoa. We observed a lower pregnancy rate in men with less than 5 millions moving spermatozoa. Under 1 million of total spermatozoa, pregnancy rate is very low (2.3%): it is established for higher values, obtaining the best results between 10 and 20 millions of total spermatozoa (10.5%) and a little reduction over 20 millions (8.3%). CONCLUSIONS The evaluation of spermatozoa total number and also their motility does not present any prognostical significance as to the pregnancy rate in intrauterine insemination for male factor infertility.