This study reports the evidence of women with a diagnosis of manic-depressive psychosis, from two standardized locus of control scales: Rotter's Internal-External scale and Reid & Ware's 3-Factor Internal-External Scale. The study compares a patient sample with a 'normative' group reported previously in the locus of control literature. A further comparison between subjects with a history of depression only, and subjects with a history of mania and depression, is also reported. Findings suggest that different factors, within the global locus of control construct, each involving a different form of cognitive vulnerability, may be part of the clinical picture of manic-depressive psychosis. The implications of these findings for nursing intervention are discussed.