the reproductive activity of small ruminants is influenced by genetic and environmental factors that determine different levels of reproductive seasonality. due to the large population of goats and the genetic identity of criollo goats in the province of neuquén, in argentina patagonia, the present study was undertaken to characterize seasonal variations in male reproductive activity. during a period of one year, ten adult males were evaluated on their reproductive parameters. they were kept under extensive management conditions and natural photoperiod (41o s). body weight (pv), testicular circumference (ct), total sperm in the ejaculate (tee), percentage of males with serving capacity (pmcs) and mean effective mounts (mme) were monthly determined. the pv and ct showed a marked increase during the spring-summer period, reaching their peak (68.1 kg and 34 cm, respectively) in february, two months after the summer solstice. in the autumn-winter period, two months after testicular circumference reached its maximum development, the tee evidenced its maximum value in april (5213 millions). the pmcs and the mme varied throughout the year, reaching the highest average values (100% and 3 mounts, respectively) in autumn (april-june). the lowest average values for these variables (53% and 1.7 mounts, respectively) were registered in spring (september-november). the variables pv, ct, tee, pmcs and mme were positively correlated with each other. the reproductive activity of criollo-neuquino males exhibited a seasonal variation, showing its highest expression in autumn (april-june), and evidenced a period of low sexual activity in spring (september-november).