The determination of urinary cobalt levels has been shown to be of value in the monitoring of occupational exposure and absorption of the metal. A rapid atomic absorption spectrophotometric method for measuring cobalt in urine is described, which has been used for biological monitoring of exposed workers from different occupational groups. Highest urine cobalt concentrations were associated with the handling of cobalt containing powders in the chemical industry (median 93 nmol/mmol creatinine) and hard metal manufacture (median 19 nmol/mmol creatinine). Significant urinary excretion of cobalt was also associated with hard metal finishing and tool making activities (median 17 nmol/mmol creatinine). The study confirms the usefulness of biological monitoring in assessing the uptake of cobalt and control of exposure.