ObjectiveTo test the reliability of telephone health survey questions. MethodA telephone survey on mental health of South Australians in 1997 was re-administered to a random sub-sample of 102 respondents between 32 and 79 days after the original survey. ResultsDemographic questions (age, gender, number of adults and children in the household) showed the highest reproducibility and were almost perfect. Questions regarding health risk factors, such as smoking and drinking behaviour, showed substantial to almost perfect agreement. Co-morbidity variables were substantially reproducible where prevalence estimates were not close to zero. ConclusionsThe results were comparable to findings from similar studies associated with the Behavioral Risk Factor Surveillance System (BRFSS) in the United States. The study suggests that the telephone health survey instrument used in South Australia is reliable for estimating health conditions and behaviours in the population.