Recently, the studies on the metabolism of porphyrin in lead poisoning have been much advanced. In spite of many studies, there still remain some obscure problems concerning with the relation between metabolism of porphyrin in lead poisoning and characteristics of air-borne particles containing lead. Then, contents of the porphyrines in the urine and blood were examined on the lead-exposed workers at a work shop for a relation between metabolism of porphyrin and air-borne particles containing lead. The following results were obtained : (1) Air-borne particles which cause the acute and chronic lead poisoning are suggested the secondary particles (fume etc.) to have rather important effect than the primary particles (ground materials etc.). (2) The working career is suggested to be related to the chronic lead poisoning in a place suspended secondary particles.