There were some studies reporting an increasing incidence of testicular cancer and genitourinary abnormalities such as cryptorchidism and hypospadias whereas human sperm quality is declining. Over the last decades, there has been growing concern about the threat to human health represented by chemicals and radioactive materials introduced to the environment. In fact, testicular damage may result of the action of deleterious lifestyle factors such as the use of alcohol or drugs as well as wearing tight underwear. Moreover, it has been demonstrated that psychosocial factors such as stress and socio-economic problems may also affect reproductive function. Some authors suggest the long term exposition to pesticides, because of their estrogenic or antiandrogenic action, may explain all these abnormalities. In Slovenia, significant changes in sperm quality occurred among a population of young healthy men. During the time period 1983-1996 rapid progressive motility decreased and we observed lower sperm concentration among men born between 1950 and 1960. Moreover, during the shortterm war for independence in july 1991, we found sperm motility decreased. The causes of such deteriorations are not well-established. However not all the researchers have found changes and in the same country regional differences may exist. These modifications need to be analyzed in large multicentric studies using the same methodologies, firstly to better understand the extent of the problem and their underlying aetiologies, secondly to oppose them the right prevention or treatment. Although in humans a negative change in sperm quality does not mean automatically that it is a greater threat for fertility, we can expect that it can result at long term in some state of subfertility which supposes that increasing numbers of couples may have troubles to conceive and may require medical assistance, with its attendant psychological, economical and social costs.