A population-based case-control study of incident brain tumours in adults in Adelaide, South Australia considered possible associations of exposures to amalgam fillings and diagnostic dental X-rays with subsequent development of glioma and meningioma. The study, conducted in 1987-1990, recorded data from 110 subjects with glioma, 60 with meningioma and 417 controls. Principal findings were unexplained decreased risks for glioma associated with both exposure to amalgam fillings (age- and sex adjusted relative risk = 0.47, 95% confidence interval: 0.25-0.91; P = 0.02) and to diagnostic dental X-rays (adjusted relative risk = 0.42; 95% confidence interval: 0.24-0.76; P = 0.004), and a possible increased risk for meningioma in males exposed to dental X-rays. The choice of the unexposed comparison group is important in determining if an increased risk is associated with panoramic or full-mouth X-rays in glioma.