Two New Zealand surveys were examined to assess the robustness and reliability of the Problem Gambling Severity Index (PGSI). The PGSI cohered to a single factor in both data sets and had high internal reliability. These features held when separately considering men, women, Maori, Pacific and Asian people. Positive associations were evident between the PGSI and gambling behaviour, accessing gambling intervention services, arguing about gambling, the burden of debt due to gambling, and the co-morbidity of smoking. A meta-analysis of the two surveys establishes a prevalence of .53%. When considering 36 overseas studies this figure is adjusted to .50%. These estimates are around 20% higher than that established by the largest NZ study and 25% lower than the latest study. The use of meta-analysis is recommended to obtain a timely and accurate estimate of the prevalence of problem gambling, especially when repeating a large sample survey is prohibitively expensive.