The half-life of saliva cotinine and its accuracy at detecting light or intermittent smoking were examined. Five subjects provided daily saliva samples for 23 days and quit smoking on day 4. An average of 2.8 days was required for saliva continue to drop below the cutoff for classification as a smoker. All smokers smoked intermittently at various times after day 9. In most cases the smoking of one or two cigarettes was detected in the saliva sample on subsequent days. Saliva cotinine was sensitive to low rates of smoking and to intermittent smoking.