The frequency of multiple paternity in 21 moor frog (Rana arvalis) egg clutches from one Swedish breeding locality was investigated using nine microsatellite loci. By genotyping on average 24 fertilized eggs per female, two different analyzes revealed multiple paternity in 14% and 29% of the egg clutches examined, respectively. In the multiply sired broods, approximately 23% of the individual eggs belonged to a second male. The observed frequency of multiple paternity was relatively high and in line with earlier amphibian studies. The evolutionary significance and proximate reason (active multiple mating or sperm leakage at communal lek) for the observed patterns remain unclear.