On the basis of theories we articulated in earlier papers (Ehlers et al 1988: Arch Gen Psychiatry 45:948-952, 1993: Depression 1:285-293), we have developed an adjunctive psychosocial intervention for patients with bipolar 1 disorder. Central to this intervention is the establishment of regularity in daily routines. In this report, we present data from a controlled investigation comparing this new treatment, interpersonal and social rhythm therapy (IPSRT), with a conventional medication clinic approach. Despite comparable changes in symptomatology over a treatment period lasting up to 52 weeks, subjects assigned to IPSRT (n = 18) show significantly greater stability (p = .047) of daily routines with increasing time in treatment, while subjects assigned to the medication clinic condition (n = 20) show essentially no change in their social routines as measured by Social Rhythm Metric (SRM-Monk et al 1990: J Nerv Ment Dis 178(2):120-126) score. We conclude that IPSRT is capable of influencing lifestyle regularity in patients with bipolar 1 disorder, with the possible benefit of protection against future affective episodes.