Two experiments were conducted to assess the bioavailability of lysine from a liquid lysine product (LLP; 60% lysine) relative to crystalline L-lysine.HCl. In the first experiment, four groups of five chicks were fed a lysine-deficient basal diet containing corn, soybean meal, and feather meal or the basal diet supplemented with 0.1 or 0.2% lysine from L-lysine.HCl or LLP from Day 8 to 22 posthatching. Weight gain and feed efficiency responded linearly (P 0.05) in the response to lysine from L-lysine.HCl or LLP. Experiment 2 was conducted using a lysine-deficient basal diet containing corn, peanut meal, and feather meal, and all diets were fed to five groups of five chicks from Day 8 to 21 posthatching. Treatment additions again consisted of 0.1 or 0.2% lysine from L-lysine.HCl or LLP. Weight gain and feed efficiency responded linearly (P 0.05) in the response to lysine from L-lysine.HCl or LLP. These data indicate that lysine from LLP is fully bioavailable relative to lysine from crystalline L-lysine.HCl, and could therefore be used as a source of lysine in practical poultry diets.