Abstract
Only 14 species of aquatic oligochaetes occurring in inland waters of Iran have been recorded until now. Our investigations based on samples collected in 2003 and 2005 revealed the presence of six species, including five new to the fauna of Iran: Haplotaxis gordioides, Dero dorsalis, Pristina breviseta, Embolocephalus velutinus and Psammoryctides albicola. The provided checklist of Iranian aquatic oligochaetes is still very short (19 species). It is mostly represented by common, cosmopolitan species. However, taking into account the large area of the country, its mountainous terrain and peculiar hydrological network, more species may be discovered in the future.