An unreported spillage of mercury in a dental surgery resulting in four non-fatal cases of mercury intoxication by inhalation of mercury vapor is described and clinical symptoms in relation to urine mercury levels noted and discussed. The method of detection and decontamination of the mercury vapor source is reported, and suggestions for preventing spillage of mercury and reducing the risk of intoxication from such accidental spillage are made. Continued vigilance by all persons handling mercury is stressed.