The horizontal distribution of fungi in and around two mangrove swamps on the island of Inhaca (Portuguese East Africa) was investigated by a direct inoculation method. Some information on the physical and chemical properties of the soils was obtained to find correlations between nutrient levels, etc., and the nature of the fungus population. There is a definite positive correlation between the amount of carbon and the variety in the fungus flora, and it is suspected that the nature of the nitrogen source is important as well. Phycomycetes are almost absent but were found in great number in one sample taken somewhat further inland. Ascomycetes are rare except for Aspergillus and Penicillium, and Basidiomycetes are entirely absent. Aspergillus and Penicillium are present in great variety in the swamps but relatively few species are found in the sandy soils. Fusarium is common and present in great numbers in the poorest soils. In one of the two swamps the genus Pestalotia is abundant. Few hyaline and many dark members of the Moniliales can be found in most parts of the investigated area’s. The surface vegetation shows the same amount of variation as the fungus population, but there are indications that both are influenced more or less independently by the variation of soil conditions.