Fatigue tests have been conducted to investigate the crack growth characteristics of pure titanium in NaOH solution. At ΔK≤10 MPa √(m), the crack growth rates in NaOH solution were enhanced compared to those exposed to air, while at ΔK > l0 MPa √(m), the crack growth rates in both environments were identical. Since the crack growth rates in NaOH solution were still higher after allowing for crack closure, this acceleration at lower ΔK levels was due purely to an environmental effect. The fracture surfaces at a higher ΔK regime, where crack growth rates were similar in both environments, revealed a preferentially transgranular mode. On the other hand, in the regime where the crack growth rates were accelerated in NaOH solution, cleavage-like facets were observed which increased with decreasing ΔK. Based on the results of da/dN-ΔK relationships and fracture surface observations, it was concluded that the higher crack growth rates in NaOH solution were not attributed to stress corrosion cracking (SCC), but to hydrogen embrittlement as a result of an electrochemical reaction at the crack tip.