Carbon monoxide in SN 1987A

It is pointed out that the infrared emission of carbon monoxide in SN 1987A is optically thick at early times and that the level populations fall out of thermal equilibrium at later times. A reinterpretation of the data yields masses of CO of order 10^-3^ M_sun_. A chemical scheme is advanced with which these high masses can be reproduced provided that the ejecta contain clumps of microscopically unmixed gas, occupying at least 10% of the volume.