This study investigated the water use of lactating sows (experiment 1), suckling piglets (experiment 2), weaned piglets (experiments 3, 6 and 8) and growing pigs (experiments 4, 5, 7 and 9), according to 3 specific objectives which assessed the effects of: age, live weight, feed intake and physiological status on water demand (experiments 1 to 3); different types of drinker on water use (experiments 4 to 6); dietary mineral content on water demand (experiments 7 and 8). For all classes of pig, feed intake explained between 53 and 83% of the variation in water use (P < 0.001). The relationship between stage of lactation and live weight (experiments 3, 6 and 7) was confounded by feed intake. In sows water use increased linearly in the week before farrowing (P < 0.001) which then decreased from 12.3 ± 1.10 1 the day before, to 9.3 ± 0.84 1 the day of farrowing (P < 0.001). Water use averaged 18.9 ± 0.27 1/day in a 21 day lactation. With suckling piglets, provision of water and/or creep feed between days 8 and 21 did not influence growth ( P > 0.05). Provision of creep feed reduced water use (0.22 ± 0.019 v 0.53 ± 0.035 1/litter day; P < 0.001), but water provision did not influence feed intake (34.7 ± 3.4 g/litter day; P > 0.05). Early weaned piglets (21 d) showed a disturbed pattern of water use in week 1 and water use averaged 0.94 ± 0.050 1/piglet day between weeks 1 and 3. In growing pigs, water use per unit of feed intake decreased linearly from 17 to 81 kg W and water use averaged 5 ± 0.16 1/day. Type of drinker influenced performance immediately after weaning (P < 0.001), but results with growing pigs were less conclusive. Water use from the Mono-flo nipple drinker was about twice that from 5 other types of drinker (P < 0.001). Dietary potassium (K) increased the water use of growing pigs by 1 1/day for every 1% increase in K between 7 and 15 g/kg feed (P < 0.05) , but performance was not affected (P > 0.05). With piglets water use and performance were not affected by variations in dietary K and Cl contents between 6.7 and 15.6; 1.4 and 3.0 g/kg feed respectively (P > 0.05). Growing pigs fed liquid diets utilised a supplementary water supply even though the water added to the meal exceeded ARC (1981) recommended allowances (experiment 9). Daily weight gain and conversion of dry matter improved as the moisture content of the liquid diets was increased from 67 to 88% (P < 0.05).