a1 Infestation Control Laboratory, Ministry of Agriculture, Fisheries and Food, Tolworth, Surbiton, Surrey
1. A marked sex variation in susceptibility to warfarin was found in 6-month old L.A.C. Grey mice, males being more susceptible than females. No sex difference in response was evident in young mice 6 weeks old.
2. Susceptibility to warfarin poisoning increased markedly with age in males but not in females.
3. No significant increase in mortality following warfarin poisoning occurred in adult female mice given methyl testosterone.
(Received October 10 1966)