The spermatozoa survival test (SST)--which is used in our laboratory is considered to be a relatively simple test with a large probability determining the ability of spermatozoa to fertilize oocytes in vitro. The SST reveals the percentage of motile spermatozoa after 20hr. cultivation with an oocyte. 221 sperm samples used for oocyte fertilization were analyzed and divided into four groups: normospermia (123 samples), oligospermia (19), asthenospermia (45) and oligoasthenospermia (34). The results show a significant reduction of the fertilization rate (< 35%) below the range of 40% SST in all groups. Above the value of 40% motile spermatozoa after 20hr. cultivation is the fertilization rate in all groups higher (> or = 50%). The authors recommend the SST as a part of the screening examination before the couple is admitted to an assisted reproduction programme.