This study was conducted to find out the role of the catecholaminergic terminals in the preoptic area (POA) in selection of ambient temperature in rats. The adult male Wistar rats (n = 6) were allowed to choose between three ambient temperatures (24 degrees C, 27 degrees C and 30 degrees C). Rats could move about freely from one ambient temperature to another, in a specially designed environmental chamber having three interconnected compartments, which were maintained at the above mentioned temperature. The results show that the normal rats preferred to stay at 27 degrees C both during day and night. After the lesion of catecholaminergic terminals in the POA with 6-hydroxydopamine (6-OHDA), the animals preferred 24 degrees C on the third and seventh day and 27 degrees C on the fourteenth and twenty first day after lesion. The alteration in thermal preference was associated with an elevation of rectal temperature. The study suggests that the catecholaminergic terminals of the POA play an important role in integrating behavioural and non-behavioural thermoregulatory responses, but in its absence the rest of the brain takes over some of its functions.