The functional integrity of membranes of 12 semen samples from fertile men and 60 from male partners in couples with infertile marriage was assessed by hypoosmotic swelling test, eosin vitality test and swelling/eosin test. We found a mean swelling percentage of 75 +/- 2.7 for the group of subjects with proven fertility, while a mean of 72 +/- 9.24 was found for the group of infertile subjects. An amount of less than 60% was found in 7 of the latter group and only one less than 50%. By using the "swelling/eosin" test we obtained a mean of 66 +/- 5.5 for the first group of subjects. Instead we found a mean percentage of 55 +/- 14.3 for the second group; 9 of these subjects had values between 50 and 60 percent and 11 less than 50%. We didn't find statistically significant correlation between semen parameters and the swelling test and semen parameters and swelling/eosin test. The results we obtained lead us to suppose that the swelling/eosin test is more accurate than the swelling test alone.