Lymphangiomatosis is a rare condition that involves bone, soft tissue, or viscera in a diffuse fashion. We report four examples affecting male infants and boys (aged 9 months to 11 years: mean, 5.3 years). All four cases presented with respiratory symptoms. Investigations showed chylothorax in all patients and chylopericardium in one patient. Three patients showed multiple lytic lesions in several bones on the x-rays. Imaging studies of lungs and spleen suggested lymphangiomatosis. Biopsy specimens of the parietal pleura, lung, skin, or bone revealed an increase in the size and number of thin-walled channels lined by attenuated endothelial lining. All had histological evidence of parietal pleural involvement. In addition, lung involvement was seen in three cases and skin involvement in two cases. Factor VIII-related antigen and CD31 were the most reliable immunocytochemical markers in highlighting the endothelia. All the patients had repeated thoracocentesis and pleurodesis to control chylothorax; three died within 6 to 33 months of presentation (mean, 15 months). Autopsy performed in two cases revealed additional involvement of spleen, bone, and mediastinum. Further, lymphangiectasia was seen in the liver, kidney, tests, lymph node, intestines, and adrenals.