Seasonality in milk performance and reproduction was analysed in low-input mountain farms in the Czech Republic. Two different feeding regimes were distinguished: seasonal pasture and all-year silage feeding in confinement. Seventeen pastured herds and sixteen confined herds of Czech Pied and Holstein breeds (total 12 158 cows) were included in the seven-year study. Seasonal variation of milk, fat and protein yields per lactation according to the month of calving was found in both groups of herds. The highest yields were achieved by autumn-calved, and the lowest yields, by summercalved cows (difference of 542 kg and 474 kg of milk on average in pastured and in confined herds, respectively). Higher individual daily yields (up to 2.9 kg on average) were recorded in the period between May and July than in the rest of a year. No effect of month of calving on days-to-firstservice and on days-open period was identified.