A survey of sperm concentration and morphology among petroleum refinery workers was conducted. The survey was prompted by a questionnaire study of males in a wastewater treatment facility of petroleum refinery that showed twice the rate of fetal loss during the period of employment. The cohort consisted of 34 male workers, mean age 31.6 years, employed in the waste water facility of the refinery. The comparisons consisted of 74 males, mean age 34.9 years, employed in other parts of the refinery. Each subject completed a questionnaire and underwent a physical examination concentrating on the urogenital tract. Semen specimens were collected after at least two days of sexual abstinence and were assayed for mean sperm concentration and sperm morphology. The mean sperm concentration of the cohort was 68.2 million per cubic centimeter (million/cm3) and that of the comparisons 79.9 million/cm3. The difference was not significant. The proportion of sperm with abnormal morphological features did not differ significantly, 44.5 percent in the cohort and 49.1 percent in the comparisons. These results did not change when potentially distorting effects of age, smoking, use of alcohol or marihuana, use of baths or sauna, and history of urological problems were considered. The authors conclude that spermatogenic impairment was not present in wastewater treatment workers at the time of the survey.