The study was carried out on three groups of ewes: group 1 – Polish Mountain Sheep (PMS, n=30),group 2 – prolific Olkuska Sheep (OS, n= 30) and group 3 – F1 PMS × OS crossbreds (n=30). Ewes were aged 4-5 years, weighed 60±5 kg and were milked twice a day from April to the end of August.Individual milk yield was recorded at 10 days intervals and every 30th day bulk milk was sampled to determine its mean chemical composition. During the milking period (i.e. from weaning of lambs)the highest milk yield was achieved by prolific OS while the lowest by PMS ewes (47.1 and 27.1 litres, respectively). Crossbreds yielded on average 31.2 litres of milk, i.e. by 4.1 litres more than PMS ewes. In the milk from first sampling the highest protein content was found in PMS, followed by OS and F1 crossbred ewes.