Faecal egg counts per gram of faeces (EPGs) were measured over a period of two years (1995 1996) in Polish Wrzosowka ewes. Measurements were made at monthly intervals. The first examination in each years was conducted before the start of the grazing season, while the rest of the samples were collected during grazing season. The animals were drenched in May 1996 but not in 1995. EPG were estimated by modified McMaster method and were transformed by log (EPG + 1) prior to analyses. Infective larvae of nematode species were identified according to the method described in Anonymous (1986). Meteorological data were collected to evaluate the influence of rainfall and temperature on the faecal egg counts. The MINITAB programme was used to calculate the correlation coefficient between EPGs in different sampling. There was substantial variation among individuals in their EPG. Several nematode species were present; however two nematode genera were dominant: Haemonchus contortus and Trichostrongylus sp.. The mean count and the composition of the nematode population was influenced by the weather conditions. H. contortus was the main egg producer during the period of high mean counts when the temperature and rainfall were highest. The correlations between EPG on successive sampling were positive and nearly always significant.