An evaluation of atabrine suppression under field and combat conditions is attempted. The malaria rate in itself is of little value since the total amount of malaria to be suppressed is unknown.
The percentage of men showing positive smears (very few parasites) when on good suppression (checked by atabrine levels) is assumed to be roughly indicative of the amount of malaria in this group of men. An index of 14% positive was obtained in a group of whom 80% relapsed with attacks of vivax malaria within two months after stopping atabrine. This relationship is true only if the smears are made on individuals who have had few or no previous attacks of clinical malaria.
A combination of careful history taking, determination of atabrine levels, and examination of smears showed that at least 98% of the men in strenuous combat were protected by 1.0 gm. atabrine per week. This was usually taken in 2 doses of 0.5 gm. each. No data on 0.6 gm./wk. from troops during strenuous combat is available. Sample histories showing the difficulties of administration are given.