Abstract: The U content of cassiterite (SnO₂), wolframite (Fe,Mn)WO₄, and various sulphides from two localities in the Cornubian batholiths of south-west England has been investigated. Cassiterites showed concentrations of U between 0 and 6 ppm with the higher concentrations corresponding to the darker colour bands. Sulphides contained no detectable U using the fissiontrack method, but high concentrations relate to micro- veining. This veining was also evident in associated wolframite and appeared to have a composition similar to an iron-arsenate mineral associated with the alteration of arsenopyrite. Wolframite exhibited a wide range of U concentrations with sharp zonation and several generations of ore deposition within one crystal. The U was not, however, associated with either the iron- or manganese-rich phases.