Abnormally low tyramine test values are known to be markers for vulnerability to unipolar, but not bipolar, endogenous depression. In the present study, 37 women with recent postnatal depression (25 major, 12 minor) and 22 puerperal controls with no depressive disorder, all assessed by Schedule for Affective Disorder and Schizophrenia (SADS-L) interview, together with I7 other controls, underwent the test. No significant differences in tyramine sulfate output were demonstrated between the different groups. Those subjects with endogenous features according to Newcastle score (n = 7) or Research Diagnostic Criteria (RDC) (n = 6) also had normal output. Thus, the tyramine test does not appear to be a useful marker for vulnerability to postnatal depression. Over half the subjects recalled that their postnatal depression had started in the first 2 weeks postpartum. Of the total of 62 postpartum subjects interviewed with the SADS-L, ten recalled a period of euphoria in the first postpartum week, which met RDC for hypomania and eight of them went on to become depressed postnatally. An additional patient from the total group was hospitalized with mania.