ABSTRACT:The purpose of this study was to analyse the influence of different external air temperature on changes in the air temperature of housing environment in the farrowing house for sows and consequent changes in selected parameters of performance in purebred Landrace sows and gilts. Raw data were analysed for 236 litters. The litters were born from October 2004 to March 2006. Air temperature in the farrowing house was monitored in the sow's living zone and was closely related to changes in external air temperature (P < 0.01). At the optimal internal temperatures for lactating sows (16-22°C) during mild winter the lowest incidence of stillbirths (9.92%) was detected, whereas at high internal temperatures (above 28°C) the incidence of stillbirths was 11.32% (P < 0.01). The lowest average daily weight gain was recorded during mild winter (P < 0.05).