Relatively little is known of the chronic effects attributable to the ingestion of inorganic components such as uranium and silicon. Although ingestion of large amounts of U can cause acute renal damage through a chemical effect, studies on humans have typically considered inhalation the route of exposure. We investigated the association between drinking water concentration levels of U and Si, and microalbuminuria, a sensitive biological indicator of renal dysfunction. Linear regression analysis revealed a statistically significant association between U cumulative exposure index and albumin per mmol creatinine (P = 0.03). No such significant relationship appeared for Si, although a positive trend was witnessed. Since normal but increasing levels of microalbuminuria were observed at U concentration levels below the Canadian Maximum Allowable Concentration (MAC), it is suggested that further study be undertaken.