Creep-fatigue crack growth behaviour of a Type 304 stainless steel, a quenched 2$r-1 Mo steel, Hastelloy X, a Ti-6242 alloy, and a low carbon steel under different reversed loading patterns (P-P, C-P and C-C) were investigated in air and a vacuum environment. The results are discussed in the light of fracture mechanics and fractography. Crack growth rates for all of the materials tested were successfully correlated in terms of the cyclic J integral range (AJ) irrespective of the loading patterns. In the low growth rate region, where fatigue fracture was predominant, crack growth rates of all the materials were about the same for the same value of AJ. On the other hand, growth rates were somewhat different, depending on the creep ductility of the material in the region of high growth rate, where creep fracture was predominant. Materials with lower ductility exhibited higher growth rates for the same AJ values. Differences were insignificant between the crack growth rates in air and vacuum and were consistent with the small differences observed in the fracture surface morphology in the two environments. NOMENCLATURE a, a, = semi-crack length, initial semi-crack length da/dN =crack growth rate per cycle A{ = cyclic J integral range AK = stress intensity range E = Young's modulus J = modified J integral (= C * ) P = load S = area of P-6 hysteresis loop 6 = displacement over the gauge length of specimen or at the centre of the crack o = nominal stress in static test W, B, b =width, thickness and ligament length of specimen omax = maximum nominal stress in cyclic test