A 45-year-old woman presented with a 6-week history of constipation and generalised abdominal pains. Blood biochemistry revealed a corrected serum calcium of 4.99 mmol/l, phosphate 0.82 mmol/l, and intact parathyroid hormone (i-PTH) of 0.2 pmol/l (normal range 16.1 pmol/l). Serum parathyroid hormone related peptide (PTH-rP) was 5.3 pmol/l (normal range <1.8 pmol/l). Computed tomography demonstrated an 11.0×11.6 cm ovarian tumour with cystic and solid areas and high vascularity. The patient was treated with i.v. saline and disodium pamidronate. Over the course of 3 days the serum calcium fell to 2.42 mmol/l. The patient underwent laparotomy and the tumour was excised intact. Histopathology was consistent with a small cell undifferentiated carcinoma of the ovary. Exploration at the time of the operation revealed no evidence of metastases and no invasion of the tumour capsule or local lymph nodes. The patient is now well, normocalcaemic and has no evidence of recurrence 8 months postoperatively. Small cell carcinoma of the ovary is rare and can also cause inappropriate ADH secretion whilst small cell carcinoma of the vagina has been associated with ectopic Cushings syndrome. The prognosis of hypercalcaemia of malignancy is extremely poor. This case illustrates an unusual cause of malignant hypercalcaemia in which the outcome of treatment has so far been unexpectedly favourable.