The firing rates of single neurons were recorded in the septal and preoptic areas of unanesthetized rabbits during brief periods of ambient heating. The temporal response for neurons responsive to ambient temperature were calculated as the interval of time between the onset of heating and the point at which the unit's activity reached 63% (i.e. 1-1/e) of its total change in activity. Thirty-one neurons were isolated in 5 rabbits. Fourteen neurons were facilitated. 10 were inhibited and 7 were unaffected by heating. Temporal responses ranged from <5 to 122s. The authors observed a bimodal relationship in the number of neuronal responses to ambient temperature vs temporal vs temporal response: a sharp 0- to <10-s peak comprising 22% of all responses and a relatively broad peak with a mode of 60 to <70s. These data resemble the temporal response patterns of thermally excitable neurons throughout the central nervous system.