Abstract: Forty four species of yeasts and filamentous fungi were recovered from 60 wastewater samples collected monthly from 5 steps of treatments for one year (from April-2008 to March-2009). Regarding species richness Aspergillus and Penicillium revealed the broadest spectra of species. Sixteen species of Aspergillus and ten species of Penicillium. Four other genera were also represented by more than one species and these were: Fusarium (4 species), Trichoderma (3 species), Mucor and Paecilomyces (two species each). Nine genera were represented by one species and these were: Acremonium, Blastomyces, Geotrichum, Humicola, Hypomyces, Rhizopus, Scopulariopsis, Syncephalastrum and Zygorhynchus. M. circinelloides, G. candidum A. flavus, A. niger and F. oxysporum showed high frequency of occurrence. A. fumigatus, A. ochraceus, A. oryzae, P. expansum, P. chrysogenum, T. harzianum and Z. moelleri showed medium frequency of occurrence. Remaining species occurred in low or rare frequency. The highest species diversity (15 species) was recorded during November while the lowest (10 species) was recorded during the period July-September. Wastewater samples collected during February showed the highest abundance (24.0% of total count) whereas those collected during July yielded the lowest population (3.9% of total count). The greatest count (53 CFU/ml) was recorded in samples of the fourth step which were collected during February, whereas the poorest one (0.4 CFU/ml) was recorded in the samples collected from the fifth step during July. The highest numbers of genera (14) and species (41) were isolated from the second step, while the lowest number of genera (9) and species (28) were isolated from the fifth step proving that the wastewater treatment markedly reduced the number of inhabiting fungi and spectra of genera and species. The number of genera and species also fluctuated monthly within each step of wastewater treatment. Key words: Fungi, sewage, wastewater, diversity, fluctuation.