The tropomyosins (Tms) are a family of actin filament binding proteins that possess a simple dimeric alpha-helical coiled-coil structure along their entire length. Our knowledge of Tm structure and function has greatly expanded since they were first discovered in skeletal muscle almost 65 years ago. In multicellular organisms they exhibit extensive cell type specific isoform diversity. In this essay we discuss the genetic mechanisms by which this diversity is generated and its significance to actin-based cellular functions. (C) 2011 Elsevier Inc. All rights reserved.