The study was designed to test the hypothesis that whole cells can be carried as an aerosol in the pneumoperitoneum during laparoscopy. Twelve patients undergoing laparoscopic surgery for benign and metastatic disease were included in the study. Throughout the 12 procedures, the smoke and the gas of the pneumoperitoneum was evacuated through 17 filters. Twelve filters and the tubing were washed. The liquid was centrifuged and stained immunocytochemically to identify the cells. Five other filters were also photographed with an electron microscope. On immunocytochemistry, nine of the twelve samples were identified as mesothelial in origin and the electron micrograph show many other cells stuck to the filter which appeared to be blood cells and mesothelial cells. Malignant cells were not conclusively identified, but ethical considerations prevented any intentional coagulation of malignant tissue. The presence of whole identifiable cells in the pneumoperitoneum could partly explain, port site metastasis after laparoscopic surgery for cancer.