We examine the prevalence of hypomania on day 3 postpartum using two self-report mania scales: The Highs Scale and Altman Mania Rating Scale (AMRS). 279 women were recruited from postnatal wards and completed the questionnaires on day 3 postpartum. The scales show good correlation, however, 11% of women meet the suggested threshold for caseness on the Highs Scale and 44% on the AMRS. Hypomanic symptoms are commonly experienced in the early postpartum. Although there is some evidence that the Highs Scale might be conservative, the AMRS likely overestimates hypomania in the postpartum. The definition of what constitutes 'a case' of postnatal hypomania requires further validation against clinical interview and ability to predict variables of clinical importance. Mania scales developed in bipolar disorder populations must be specifically validated for postpartum use.