The growth performance of tom turkeys maintained in closed and open confinement housing was examined. Treatments were initiated on the day of hatching and consisted of constant light intensity of 1, 11, 110, or 220 lx in an enclosed house or sunlight supplemented with 11 or 220 lx at night in an open-sided house; all treatments received a total of 23 hr of light each day (23L:1D). Body weight, feed conversion, mortality, leg abnormalities, and final testes weight were recorded. Growth performance at marker age was not significantly different among treatments except for a heavier 18-week body weight in the open-confinement group given sunlight only (DL) and, in the closed confinement, a better feed conversion in the 11 lx treatment (C11) than the 1 lx treatment (C1) at 22 weeks of age. There was no apparent relationship between light intensity level and leg abnormalities but 22-week testes weight increased as light intensity increased. It was concluded that within closed confinement a constant light intensity of 1 lx resulted in an inferior growth performance, whereas 11 lx was sufficient to allow a growth performance similar to that obtained with 110 or 220 lx. In open confinement, supplemental artificial light at night of 11 or 220 lx did not result in an improved growth performance from birds on natural daylengths.