Body temperature and sleep are closely related. In addition, thermoregulatory responses and sleep suffer important changes with advancing age, due at least in part to modifications in melatonin and serotonin secretion. The present work analyzed activity-rest and temperature rhythms as indicators of sleep-wake cycles in young and old animals and the therapeutic effect of melatonin and tryptophan on age-related sleep disorders. Young and old ring doves (3–4 and 11–13 years) kept under a 12/12 LD cycle were treated for 3 days with melatonin and tryptophan with a dose and administration schedule with known activity to improve nocturnal rest (Bas Clin Pharmacol Toxicol., 100:258-268, 2007; Phys Behav. 90:576-582, 2007). Circulating melatonin and serotonin levels, motor activity and core and peripheral body temperature were measured. In both groups, core and peripheral temperature was always higher during daytime than during night. The amplitude of the core temperature rhythm was reduced in old animals, which also showed an earlier temperature dawn rise. Melatonin administration raised the circulating levels of melatonin and serotonin in both groups and tryptophan increased serotonin levels in old birds. Melatonin and tryptophan lowered core temperature and increased peripheral temperature in the two groups. The nocturnal activity was also reduced when compared with control values after the treatments. In conclusion, melatonin and tryptophan are involved in the thermoregulation and activity-rest rhythms of ring doves and may act as potential factors to improve the age related sleep and thermoregulatory disorders. Supported by Junta de Extremadura (3PR05A053).