Influence of light, dietary amino acid levels, feeding space, and ambient temperature on male broiler body weight, feed efficiency, percentage abdominal fat, and incidence and severity of leg abnormalities was studied in two experiments. Broilers subjected to intermittent light (1 hr on:2 hrs off) had heavier 49 day body weights, and similar feed efficiencies than birds given continuous illumination. Feeding high [106 and 114% of NRC for lysine and total sulfur amino acids (TSAA), respectively] versus low (100% of NRC for lysine and TSAA) amino acid diets, improved body weight and feed efficiency at market age. Providing broilers with increased feeding space (from 1.47 to 2.94 cm/bd) resulted in improved body weight at market age. Birds under high ambient temperatures (29 to 26° C) had significantly higher feed efficiencies at four weeks of age than those given low temperatures (29 to 18° C). However, at market age broilers provided low temperatures had significantly greater gains with similar feed efficiencies. Birds fed high amino acid diets had significantly more abdominal fat than those given low amino acid diets. Light, feeding space, ambient temperature and relative humidity had no significant effect on percentage abdominal fat. Broilers provided intermittent light had significantly fewer and less severe leg abnormalities than birds under continuous illumination. Dietary amino acids, ambient temperature and relative humidity had no significant effect on the incidence or severity of the leg disorders. / Master of Science