The Hb levels of W.A.A.F. personnel entering the service is about 95% (s.d. 9.22) on the standard Haldane scale. After about 6 mos. service, the level is about 103% (s.d. 9.12) and is maintained thereafter. The normal mean value of [female][female] of this age group is probably at least 103%. The improvement is probably due to the high Fe intake of the personnel.