A case of subcutaneous splenosis in the abdominal wall of a 23-year-old oligophrenic man is reported. Further, the most important features of splenosis in various localisations are provided. The patient presented with a well-demarcated 8x7x5 cm subcutaneous tumour in the left inguinal area closely above the scar after a previous operation for hernia. The lesion simulated clinically a hernia or a tumour due to its large size and location. Additionally, no history could be taken from the patient due to his mental handicap. The diagnosis of splenosis was established histologically.