Postnatal depression has been estimated to affect over 10% of women with sequelae for the mother, marital relationship, and infant’s psychological development. 1 Depression can be severe and resistant to psychotherapy and antidepressant drugs. Therefore, safe and rapidly effective therapies are needed, 2 with likely association to the cause of depression. Oestrogen has been shown to be effective in the treatment of postnatal depression. 3 We report two consecutive cases fulfilling the ICD-10 criteria of depression with postpartum onset admitted to the psychiatric duty outpatient unit who responded successfully to sublingual 17- oestradiol monotherapy. We measured serum oestradiol by radioimmunoassay at baseline and weekly during follow-up. The treatment effect was evaluated by the 10-item Montgomery-Asberg Depression Rating Scale (MADRS), scores 0–6. A 30-year-old woman (case 1) had no personal or family history of mood disorders, and the relationship with her husband was stable. During the second week after delivery of her first baby she reported anxiety and sleep disturbances. Over the subsequent weeks she became more depressed, and reported inner tension, irritability, broken sleep, reduced appetite, and concern about her baby. Her family physician prescribed oxazepam 15–30 mg and counselling support was given with only temporary help. 2 months after delivery, the