A neutron-activation method for the determination of rhenium in geological materials is described. Radiochemical separation, using Re-carrier and liquid-liquid extractions, yields (186)Re in a state of radiochemical purity. The gamma-ray activity of the radionuclide is counted with an NaI(Tl) crystal scintillation detector, and the chemical yield is determined spectrophotometrically. Results for the contents of rhenium in the standard rock W-1 and in nickeliferous lateritic profiles are reported. Particular problems arising in neutron-activation analysis for rhenium in lunar surface materials are discussed.