Heat and moisture production (HMP) values are used to size ventilation fans in animal housing. The HMP values that are currently published in the ASABE standards were from data published in 1975. This study is one of a series of studies being conducted to update the HMP values for the ASABE and ASHRAE (American Society of Heating Refrigeration, and Air Conditioning Engineers) Standards. This study focused on the HMP measurements on nursery and growing pigs in the weight range of 8 to 44 kg. Ninety-six nursery pigs were randomly assigned to one of 24 pens (4 pigs /pen) and subjected to one of four temperatures between 25 and 35°C. Forty-eight growing pigs were penned in groups of 2 and subjected to one of four temperatures between 18 and 33°C. Heat production rate (HP) was determined using indirect calorimetry methods, after the animals were acclimated for a minimum of 1 week to a particular temperature. Each measurement was made on a pen of animals (either 2 or 4 pigs/pen) over a 21-hr period. It was determined that HP decreased and moisture production (MP) increased as environmental temperature increased. In the nursery age piglets, the level of feed consumption had a greater impact on HP than temperature. Dynamic measurements showed a diurnal HP pattern; HP was higher during light period than during dark period, with an immediate increase as the lights were turned on.