Biological monitoring plays a significant part in the assessment of occupational exposure to lead. The method basically comprises determinations of blood lead concentration and of one of early toxic-effect biomarkers: the level of either zincprotoporphyrin (ZnPP) in blood or deltaaminolevulinic acid (ALA) in urine. However, biological monitoring is conducted only in 25% of all industrial plants, where the employed technological processes are the source of occupational lead exposure. The project that has been implemented by the Nofer Institute of Occupational Medicine, Lódź, Poland and Outpatient Clinic for Occupational Health, Poznań, Poland, since 1997 made it possible to assess the dynamics of lead exposure in one of the largest battery plants in Western Poland. Based on the analysis of blood lead determinations in lead-exposed workers, the authors could trace the effectiveness of the project aimed at reducing lead exposure in the plant. The findings revealed that the preventive measures applied over the years 1997-2005 resulted in a considerably decreased percentage of blood lead concentrations exceeding the relevant BEI (biological exposure index) value of 500 microg/l: from 19% in 1997 to 1% in 2005. Such a high effectiveness of the project can be mostly attributed to a successful cooperation between the occupational physician, in-plant occupational health services, and the employer. They were all actively involved in a wide-range of activities for workers' health protection and workplace health promotion.