The fluorine concentration in seventy‐one reference samples of geological interest has been determined using fast‐neutron activation analysis. The reaction involved [19F(n, α)16N] uses accelerator‐derived neutrons produced by bombarding a Be target with 3 MeV deuterons. The gamma radiation associated with the decay of16N (t1/2 = 7.13 s) is counted and for the irradiation conditions used there are no serious interferences. The advantages of this technique over other schemes of fluorine determination are its simple procedure for sample preparation, speed, high sensitivity and non‐destructiveness. A comparison of the data obtained with those in the literature is highly fa