The trends for such important parameters of male fertility as seminal volume and total sperm number were assessed in men living permanently in the Greater Athens area over a prolonged period of time. To this end, the records of three andrological laboratories employing the same method for semen evaluation were analysed retrospectively. Out of 23,850 men examined from 1977 to 1993 (17 years) for couple subfertility, a total of 2385 (10%) were selected for evaluation by a randomization procedure. Analysis of the data included (i) estimation of mean seminal volume and total sperm number per year, (ii) assessment of percentage frequency distribution of each seminal parameter and (iii) evaluation of seminal volume and total sperm number changes in relation to the year of observation and age of the subjects. A significant decrease (P < 0.01) of total sperm number was observed over the years with a mean (+/-SEM) of 154.3 +/- 19.2 x 10(6) at the beginning (1977), dropping to 130.1 +/- 13.3 x 10(6) in the final year (1993). Mean seminal volume was lower in the final year of observation, but its difference from the initial year value was not significant. Frequency distribution analysis showed a marked decline in the 240-400 x 10(6) sub-set of the range of sperm number values from 16.9 +/- 4.5% (1977) to 10.6 +/- 1.6% in the final year (P < 0.01). Multiple regression analysis of seminal volume, total sperm number, age and year of assessment revealed a significant decline of the two seminal parameters along the years of observation (P < 0.05 and P < 0.0001 respectively). Over the same period, a marked deterioration of some air pollution indices was observed in that area. It is concluded that in this racially and ethnically homogeneous sample of men, living under the same environmental conditions, a significant decline in seminal volume and total sperm number occurred over the 17 years of observation.