The cause of histological damage of Faunus ater (gastropod mollusk) gonad has been identified in the samples from two rivers, namely Bale River and Reuleng River which flow through residential, agricultural and industrial areas. Heavy metal concentration within the tissue of Faunus ater is analyzed with Atomic Absorption Spectrophotometer (Shimadzu AA 630). Meanwhile, the histological damage on gonads is observed microscopically. Afterward, the damage levels obtained from the two respective rivers are then compared and analyzed with t-test. The results confirm the histological damage occurred in the gonads of Faunus ater collected from the two rivers. Gonadal damage of female Faunus ater from both rivers are found to insignificantly different, observed by the number of developed and damaged Oocytes. It is also found that the gonads of male Faunus ater collected from Bale Riverl, have higher quantity of spermatogenic cells, in which they experience more necrose than the ones from Reuleng River.