1. (1) As a preliminary to operations intended to eliminate the major parasitic diseases, a health, nutrition and parasitological survey was made in Keneba, a village of 710 inhabitants in West Kiang, Gambia, during 1950-51. 2. (2) The villagers depend for food very largely upon their cereals and foods of animal origin are rarely eaten. There is a marked seasonal variation in food supplies, giving rise to a regular “hungry season.” 3. (3) Body weights of adults were below those of racially comparable groups and the growth pattern of children was considered to-be probably sub-optimal. Clinical signs attributable to deficiency of vitamin B complex factors were found to be common. 4. (4) Malaria was found to be hyperendemic. P. falciparum predominated but P. malariae was seen in 8.5 per cent. of films. While some degree of immunity or tolerance is undoubtedly established, this appears to be a precarious one liable to break down under conditions of stress such as pregnancy. The inter-relationships of nutrition and malarial immunity are discussed. 5. (5) Approximately one-third of the population was found to be infected with A. perstans and one-third with W. bancrofti. Possible reasons for the absence of evidence of filarial infection in infants and young children are discussed and its apparent inverse relationship to malaria noted. 6. (6) Trypanosomal infection was found in 2.5 per cent. of the people. 7. (7) Hookworm infestation was found to be common, rising to over 90 per cent. in the 6 to 10 years age-group, but loads were generally light. Ascaris and Taenia were found infrequently. 8. (8) Anaemia was found to be almost universal, haemoglobin levels being lowest in the 2nd year of life. In males the levels were found to rise steadily with age well into middle life ; in females there was a marked fall during the child-bearing period. 9. (9) Some degree of “auto-agglutination” of the blood was found in all subjects. The characteristics of this clumping of cells are described. It was not cold-agglutination, nor was it related to anaemia. 10. (10) Hepatomegaly was observed very frequently in infants, often well below the age of weaning, and in children. Its incidence, associated clinical features and pathology appeared to differ from those of kwashiorkor (as defined). The possible aetiology of Gambian hepatomegaly is discussed and it is suggested that malaria, acting in conjunction with some other factor, probably nutritional and related to the constitution of breast-milk, may be the main cause of the condition. 11. (11) Notes on the entomology of the area are added. It was not possible to make exhaustive investigations of disease vectors during the survey year. The overall impression gained from the survey and from observation at all seasons of a year is that the health of Keneba villagers is, at the best, marginal and that the reserves necessary to meet any unusual physiological or pathological stresses are small.Immunity to the effects of a variety of parasites is hardly won and precariously maintained.Although this population has maintained itself for many generations the level at which it has done so is very low and it is clear that the combined forces of malnutrition and parasitization are among the major factors limiting progress and development.