A cross sectional epidemiological study of 93 arc welders in a shipyard was conducted to observe the adverse effect of exposure to manganese welding fumes. Among them, 37 workers with paired controls were given the neurobehavioral tests. Air concentration of manganese in working place, hair manganese and platelet 5 hydroxytryptamine in both exposed workers and controls was also measured. The higher percentage of respiratory symptoms including sour throat and dyspnea in the welders were observed as compared with the controls. The results of neurobehavioral tests showed that the welders exhibited poorer performance in simple reaction time and Santa Ana dexterity tests than that in the controls. The hair manganese concentration was higher and the blood platelet 5 HT level decreased in the welders. In conclusion, symptoms in the welders might be related to the exposure of manganese. Long term exposure to manganese welding fume could cause the change in simple reaction time and Santa Ana dexterity tests. The hair manganese concentration could be used as a biological monitoring index of exposure to manganese. A cross sectional epidemiological study of 93 arc welders in a shipyard was conducted to observe the adverse effect of exposure to manganese welding fumes. Among them, 37 workers with paired controls were given the neurobehavioral tests. Air concentration of manganese in working place, manganese The higher percentage of respiratory symptoms including sour throat and dyspnea in the welders were observed as compared with the controls. The results of neurobehavioral tests showed that the welders exhibit poorer performance in simple reaction time and Santa Ana dexterity tests than that in the controls. The hair manganese concentration was higher and the blood platelet 5 HT level decreased in the welders. In conclusion, symptoms in the welders might be related to the exposure of manganese. to manganese welding fume could cause the change in simple reaction time and Santa Ana dexterity tests. The hair manganese concentration could be used as a biological monitoring index of exposure to manganese.