The myxomycete diversity of the Mezit valley and vicinity was assessed from 1999 to 2002 in the Southern Marmara region of the Bursa and Eskisehir provinces of Turkey. Of the 36 species and 12 genera listed, 22 represent new records for the valley and surroundings. The ecology of the valley is briefly discussed. A map of the study area and the checklist are available at the website http://biyoloji.uludag. edu.tr/ergul/Checklist-001.pdf.