The column abundance of OClO at McMurdo Station, Antarctica, was measured by visible absorption spectroscopy during austral spring in 1986. Observations were obtained during the day using scattered sunlight and at night using direct light from the moon. The observed total column amounts in Antarctica were about 20--50 times larger than would be expected for standard homogeneous photochemistry, suggesting that the halogen chemistry of Antarctic spring is profoundly different from such standard theoretical expectations and may play a role in the development of the springtime Antarctic ozone ''hole''. ¿ American Geophysical Union 1987