Recent pedigree studies demonstrating a possible linkage of bipolar disorder to markers on different chromosomes have included family members with major depression and cyclothymia as affected. There is general agreement that cyclothymia is related to bipolar disorder and that major depression is heterogenous. It is unclear which subtype of major depression is related to bipolar disorder. Data suggesting a relationship between delusional subtype of major depression and bipolar spectrum are presented. The data derive from a direct-interview study of 220 offspring (ages 6 to 23 years) of probands with either delusional or nondelusional major depression and normal controls. The children of delusional as contrasted with nondelusional probands had nearly a threefold increase in cyclothymia, were more often described by health professionals as hyperactive, and had increased school and social impairments. These findings in children replicate earlier findings in adults on the possible relationship between delusional depression and bipolar disorder and its spectrum. The findings must be considered tentative, however, because of the small sample of children in the subgroups of interest.