Gelatinous degeneration of the peritoin is an unusual disorder which inevitably takes the surgeon by surprise during laparotomy. Three cases are reported. The diagnosis, pathogenesis, prognosis and possible therapies are discussed. The tumoral pathogenesis usually appears to be non-malignant and to originate in the ovaries or appendix. However, gelatinous degeneration of the peritoin must be viewed as a disease with attenuated malignancy. The pattern of development is slow, with repeated peritoneal recurrences. The survival time is long. Treatment is essentially surgical even when recurrences occur.