IT has been possible to obtain eight samples of whales' milk for analysis through the very willing co-operation and help of Dr. E. Downing and Mr. J. A. B. Athey, of Chr. Salvesen and Co., Leith, and Dr. J. G. Sharp, of the Low Temperature Research Station, Cambridge. Two of the samples were from blue whales (Balœnoptera musculus) and the remainder from fin whales (Balœnoptera physalus). The milks were collected after dissection of the mammary glands during the flensing operation on board Salvesen and Co.'s factory ships Southern Venturer and Southern Harvester engaged in pelagic whaling in the Antarctic. The period between the death of the whales and the collection of the milk varied from 6 hr. for sample 7 to 19 hr. for sample 4. The samples were stored in glass bottles at a temperature of - 20° C. while on board ship and ashore, before being conveyed to the Hannah Institute with as little rise in temperature as possible. At the Hannah Institute the samples were kept at 4° C. and analysed without delay. Samples 1–3 were at a temperature of - 20° C. for six to seven months and samples 4–8 for two to three months.