Abstract The linear elastic fracture mechanics approach has been applied in the investigation of the influence of 3.5%NaCI solution in distilled water on the fatigue crack growth in two aluminium alloys, high-strength RR58 and cast LM30. The effects of mean stress intensity factor and frequency have been studied also. Specially developed double cantilever beam (DCB) specimens were used and the corrosion fatigue results compared with those determined in air. It was found that, in general, at low frequencies (≃0.2 Hz) fatigue crack growth was accelerated in the solution in comparison to a laboratory air environment, but for higher values of the maximum stress intensity factor, this effect was negligible. Also, threshold values, ∆Kth, decreased in the solution in comparison to air. In particular, threshold values for RR58 appeared to be rather low and decreased still further with higher frequency. Finally, the substantial effect of the corrodent was observed only at low values of ∆K.