1. A total of 2560 male and female Ross broilers were raised to 42 days of age in a 2 X 2 treatment factorial arrangement experiment to investigate the influence of different degrees of physical activity and dietary energy on broiler performance, abdominal fat content, carcase yield and sensory quality. 2. Vertical fans were used to force the treatment birds to walk 3 to 4 times as far as the normal activity birds; birds were fed a normal and a high energy diet (12·55 compared with 13·81 MJ ME/kg) with the same energy/protein, energy/lysine and energy/methionine + cystine ratios. 3. High activity birds had greater body weight ( + 4·1%), food intake ( + 5·1%) and ME intake ( + 5·1%) than normal activity birds. Birds receiving high energy diet had a lower food conversion and food intake than birds receiving normal energy diet. There were no significant differences in body weight or ME intake between birds with different diets. 4. Slaughter yields, both absolute and relative to live body weight, were affected by activity or dietary energy to varying degrees. Breast meat was increased with more activity. The absolute weight of abdominal fat was independent of activity and in males the relative weight of abdominal fat was decreased in high activity birds. 5. Different degrees of activity and dietary energy had only minor influences on broilers' sensory quality.