The activity of mould and yeast population on the surface of Satsuma mandarin was studied at four temperatures (2, 4, 10 and 20°C) and two relative humidity (RH) levels (80 and 93%) on fruits washed and on fruits washed and treated with a fungicide mixture (1200 ppm thiabendazole + 800 guazatine + 400 ppm prochloraz), stored for 20 and 40 days. The lowest final microbial counts (CFU) were for the fruits treated and stored at 2°C and 93% RH and the highest counts were for fruits stored at 20°C and 93% RH regardless of fungicide treatment. Throughout the storage period, yeast and Cladosporium spp. were predominant in the microbial counts and generally showed reducing trends. The fungicide treatment was very efficient and persistent. The absence of antifungal treatment and the increase of RH levels caused a greater rise of CFU than the increase of the storage period or temperature. An increase in the CFU values with the increase of RH was observed in untreated fruits. The treatment of Satsuma fruits with the fungicide mixture, followed by cold storage at 2°C and 93% RH, extended the storage period at least 40 days.