The aim of the studies was to analyse the relationship between the FCM yield in 1067 lactations and the length of the service period, length of intercalving period and insemination index. The research was carried out on cows bred in 6 farms. Indices of fertility and milk yield of particular cows were calculated from breeding record books. It was found that milk yield influenced the indices of fertility. The insemination index, length of the service period and the intercalving period were increased with an increase of FCM yield in the lactation. Correlation coefficients were positive and statistically significant.