This study aimed to investigate the relationship between age at onset and time to first pharmacological treatment in patients with either bipolar I or II disorder. A total of 146 consecutive in-patients acutely admitted from the same catchment area were included. Patients were divided into four age groups: 0-12 years (23%); 13-18 years (32%); 19-29 years (26%); and > or =30 years (18%). Mean age at first affective episode was 20.2 years (s.d.=11.8). This represents a similar pattern to the age at onset seen in out-patients in the USA. Early age at onset predicted a longer time to first pharmacological treatment (rho =-0.695, P<0.01).