We describe a new highly polymorphic DNA marker flanking the human ryanodine receptor gene (RYR1) at chromosome band 19q13.1. The marker is composed of a 25bp minisatellite sequence, a compound microsatellite (AC)(AT), and an oligo-T stretch. STS mapping of previously published markers from 19q13.1 helped to integrate the genetic and physical maps of this region. Together with D19S422, the new polymorphism forms a pair of markers closely flanking either side of the RYR1 gene which may be useful for linkage studies in families susceptible to malignant hyperthermia and central core disease.