Biological assessment of occupational exposure to cadmium in five different factories with low-level second degree usage of Cd-compounds has been carried out. In 124 exposed and control male workers the following measurements, were performed: cadmium in blood (CdB) and urine (CdU), B2-microglobulin (B2M), creatinin in urine (Creat), hemoglobin (Hb) and hematocrit (Ht). Analysis of 34 pairs of workers matched according to age, smoking habits, ethnic origin and factory, established a significant difference only in CdU, the geometric means being 0.67 microgram/g Creat in the exposed group and 0.48 microgram/g Creat in the control group. Significant correlation was found between CdU x age and CdB x smoking habits. Multiple regression analysis showed that for each year increase in age CdU increased 3%, for each percent increase of CdB CdU increased 0.28%; for each cigarette smoked per day CdB increased 1.6%. It is concluded that in this type of work the low external cadmium exposure does not express itself in different CdB-levels, but only in different CdU-levels, indicating an increased body burden due to long term low levels occupational cadmium exposure. In biological assessment of exposure to Cd, it is essential to take age and smoking habits fully into account.