The wastewater and sewage sludge, which are rich in organic matter, are habitat for many groups of microorganisms, such as viruses, bacteria, fungi, algae, protozoa and worms. Many of them could turn out be plant, animal or human parasites, however in a routine analysis are almost never looked for. The main subject of the study was comparative analysis of microscopic fungal communities occurring in wastewater and sewage sludge. Additionally some physiochemical factors such: pH, Biochemical oxygen demand (BOD) and Chemical oxygen demand (COD) were determined. The samples of untreated wastewater, treated wastewater and sewage sludge were taken from four wastewater treatment plants. The pH values were generally neutral in range from 6,00 to 7,85. The BOD and COD values of wastewater were many higher before treatment process than after. The COD values of untreated wastewater amounted from 202 to 618 mg/dm, whereas BOD values - from 100 to 440 mg/dm, respectively. The COD values of treated wastewater oscillated from 42 to 66 mg/dm, while BOD values-from 10 to 40 mg/dm The quantitative analysis of microscopic fungi in studies samples showed that quantity of fungi was very different and oscillated in untreated wastewater from 31 X 10(3)/cm(3) to 167 x 10(3)/cm(3), in treated wastewater-from 220/cm(3) to 750/cm(3), and finally in sewage sludge-from 43 x 10(3)/g of dry solids to 182 x 10(3)/g of dry solids. The comparative qualitative analysis showed that the most quantitative occurred genus Penicillium, and usually occupied about 50% in all studied communities. The species Penicillium communae, P. lividum, P. vulpinum, P. janczewskii, P. spinulosum and P. granulatum were noted. Another position got a yeast fungi (30% in untreated wastewater, 13% in treated wastewater and 19% in sewage sludges). This group was represented mainly by genera: Candida (C. albicans, C. krusei), and Geotrichum (G. candidum). The third position with regard to number of isolates in communities occupied family Mucoraceae (16% in untreated wastewater, 17% in treated wastewater and 5% in sewage sludges). This group was represented by genera: Mucor (M. racemosus, M. hiemalis), Absidia (A. glauca), Mortierella (M. alpina, M. exigua), Zygorhynchus (Z. moelleri). Additionally in all studied fungal communities the dermatophytes were noted. That were fungi belonged to genera Candida, Cladosporium, Geotrichum, Rhodotorula, Acremonium, Sporothrix, Microsporum, Trichophyton.