We purified the free-radical scavenger “water soluble protein (WSP)” from broad beans. Oxidative stress, as well as diminished activity of lysosomal proteolytic enzymes, are known to induce lipofuscin accumulation in a variety of cell types. In order to clarify the roles of oxidative stress and lysosomal proteolysis in lipofuscin accumulation, human lung fibroblasts were treated with WSP. Hydrocortisone (HC) which is known to inhibit superoxide generation, was compared with WSP. Cathepsin B activity in young cells showed a decrease during cell culture from 0.203±0.013 mU/μg protein (4 weeks) to 0.067±0.018 (6 weeks) with an unparalleled increase in lipofuscin (as autofluorescence intensity, AFI/μg protein) from 1.46±0.05 (4 weeks) to 1.55±0.04 (6 weeks). Similarly, the activity in old cells exhibited a decrease from 0.208±0.013 mU/μg protein (4 weeks) to 0.043±0.005 (6 weeks) with an unparalleled increase in lipofuscin from 2.11±0.06 AFI/μg protein (4 weeks) to 2.27±0.05 (6 weeks). Young cells treated with WSP (1.25 μg/ml) for 6 weeks showed increased cathepsin B activity (0.118±0.009 mU/μg protein) as compared to the control, but the activity in WSP treatment for 4 weeks decreased by 89%. Young cells treated with HC (5 μg/ml) were equal in cathepsin B activity to the control. On the other hand, old cells treated with WSP for 4 weeks exhibited the decreased activity (0.179±0.008 mU/μg protein). In contrast, HC treatment for 4 weeks increased the activity (36%). WSP treatment for 6 weeks was effective in reducing lipofuscin accumulation in young (25% decrease) and old (57%) cells as compared to the control. Similarly, HC treatments were more effective in reducing lipofuscin accumulation in young cells for 4weeks (31% decrease) and old cells (63%). The present results show that the free-radical scavenging in the cultured fibroblasts reduced the lipofuscin accumulation.