The seaweed genus Fucus is a dominant component of intertidal shores throughout the North Atlantic and North Pacific and has been the focus of considerable developmental, ecological, and evolutionary research for the past century. Here, we present details of 21 expressed sequence tag-derived simple sequence repeat markers (microsatellites). All 21 were polymorphic for F. serratus, which also display considerable cross-reactivity with the sister species F. distichus (18) and the more distantly related F. vesiculosus (13), and F. spiralis (5). © 2008 The Authors.