Stellar associations and complexes in M33

The distribution of blue stars in M33 was investigated using UBV plates obtained by the 2-m RCC telescope of the Rozhen observatory. About 460 OB associations were selected. The star content, size distribution, and mean size (about 80 pc) of these associations confirm their identity with the OB associations in the Galaxy and in the Magellanic clouds. The genuine OB associations form groups of two or more members with a length scale of 250 pc, their boundaries coinciding with the OB associations described by Humphreys and Sandage (1980). The star complexes unify a group of associations, H II regions, and H I peak distribution. (I.S.)