Abstract Our measurements noticed elevated iodine concentration in precipitation due to volcanic activity. The concentrations determined in two regions of the Czech Republic increased significantly during the passage of dust cloud from Icelandic volcano Eyjafjallajökul over the sampling areas. Iodine concentration in the rainwater was up to 6.68μgdm−3 during the critical period between 16 and 20 April 2010. Measured levels were up to six times higher than background values. The increased concentrations decreased to the usual values within approximately two weeks.