A total of 4,800 broiler chickens of one commercial genotype were used to study the interrelated effects of two lighting treatments (green fluorescent vs. incandescent), three weekly rates of ambient temperature decline (4.5, 3.5, 2.0 C), and starter/finisher diets with four levels of dietary energy (3,100/3,300; 3,000/3,200; 2,900/3,100; and 2,800/3,000 kcal/kg metabolizable energy). Lighting and ambient temperature treatments had no significant (P greater than .05) effects on percentage mortality, feed conversion ratio, body weight, and monetary return. The highest dietary energy regimens resulted in the heaviest body weights, best feed conversion ratios, and the highest monetary returns. A lighting treatment x diet interaction occurred for female mortality to 42 days but was considered of minor importance. A lighting treatment x diet interaction for feed conversion provided evidence that low temperatures had a more pronounced depressing effect on broiler chickens fed low energy diets. A second order interaction for 42-day male body weights provides evidence that male broiler chickens may be less sensitive to lower ambient temperatures if fed higher energy diets under incandescent lighting compared with those fed lower energy diets under green fluorescent light.