William Compston is renowned for his contributions to isotope geochemistry and geochronology. He was a pioneer of the technique of total rock rubidium–strontium dating and has been responsible for much of the systematic geochronology of the Australian continent. He has made major contributions to cosmochemistry including successful rubidium–strontium dating of the first Apollo 11 lunar mare basalts, the strontium isotope chemistry of mare basalts generally and discoveries of isotopic anomalies in magnesium and titanium from the Allende meteorite. These latter discoveries have important implications for the origin and evolution of the primordial solar nebula. Recently he designed and constructed an ion-probe microanalyzer possessing unique resolution and sensitivity. This has been used successfully to measure lead–uranium ages on zircons and to characterise the ages and provenance of the source materials of granitic plutons.