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The effects of season in a tropical climate and parity on lactation performance of 106 Large White sows over several reproductive cycles (301 lactations in total) were studied in Guadeloupe (French West Indies, 16°N latitude, 61°W longitude) between January 1999 and March 2003. Two seasons were determined a posteriori from climatic parameters recorded continuously in a station close to the experimental unit. During the warm season, ambient temperature and relative humidity averaged 23-5°C and 0-831, respectively. In the hot season, the corresponding values were 26-0°C and 0-834, respectively. Over the 28-day lactation period, average daily food intake (ADFI) was lower (P < 0-001) and live-weight (LW) loss was higher (P < 0-05) during the hot season than during the warm season (3-9 v. 4-7 kg/day and 17 v. 12 kg, respectively). Growth rate and mean LW of piglets at weaning were lower (P < 0-05) during the hot season (203 v. 220 g/day and 7-0 v. 7-5 kg, respectively). However, the weaning-to-oestrus interval was not affected by season (5-4 days on average). The effect of season on ad libitum ADFI was less accentuated for primiparous than for multiparous sows (warm-hot 360 v. 2002 g/day). Irrespective of the season, ADFI was lower (P < 0-01) and piglet growth rate tended to be lower (P < 0-2) in primiparous than in multiparous sows (4-0 v. 4-4 kg/day and 205 v. 215 g/day, respectively). Moreover, the percentage of sows that returned to oestrus later than 5 days after weaning was higher in primiparous than in multiparous sows (25 v. 2%, P < 0-001). This study confirmed the negative effects of the hot season on performance of lactating sows raised in a humid tropical climate; the effects of season are dependent on parity number.