This study aimed to compare disease factors, in terms of morphological, molecular and ultrastructural characters, for nosemosis in honey bees in Turkey. Nosema ceranae Fries et al., 1996, a pathogen of Apis mellifera was detected with light microscopy and PCR-based methods. Then, its spore ultrastructure was studied with transmission electron microscopy (TEM) to compare with the known ultrastructure of isolates of N. ceranae from different countries. Mature fresh spores measured 4.5 x 2.5 mu m (n=50) and Giemsa stained spores 4.4 x 2.6 mu m (n=50). Polar filament had 22-23 coils, showed isofilar structure and measured 85-90 nm in diameter. Endospores measured 115-140 nm with low electron density, while exospore measured 15-30 nm. TEM studies confirmed that ultrastructure characters of the Turkish isolate of N. ceranae differed slightly from those of N. ceranae isolates from different countries. This is the first study of spore morphology and ultrastructure of N. ceranae recorded in honey bees in Turkey.