Objective: Biological monitoring and efficiency of the treatment with Cuprenil for the severe occupational inorganic lead poisoning. Materials and method: The group we studied had 20 patients suffering of inorganic lead poisoning, coming from Sometra Copsa Mica. They were hospitalized in the Occupational Medicine Hospital in Tg. Mures from July to October 2006. All of them followed a treatment with Cuprenil (penicillaminum) during hospitalization with a dose of 1g/24h divided in four equal parts. We have monitored the exposure tests and the biological effects tests. Results: Medium hospitalization period for the patients without liver or kidney failure was from about 10 to 14 days followed by a stop of exposure for lead for another 3 weeks. Abdomen colics disappeared 48-72h after the beginning of the treatment with Cuprenil and Plegomazin. Because of the serious vomiting, almost all of the patients had to be rehydrated. After the treatment, for 4 patients we had transitory increased liver tests which came back to normal levels by the end of the hospitalization. The exposure tests and the biological effects tests had significant changes without relevant explanations. Conclusions: 1.First choice in treating the occupational inorganic lead poisoning is EDTA (ethylenediaminetetraacetic acid). It can be replaced with Cuprenil (with a dose of 1g/24h). 2. The favorable evolution is slower in this situation and the exposure tests and the biological effects tests have an odd fluctuation. 3. The side effects of Cuprenil are more frequent than the side effects of EDTA.