In three patients with cardiac myxoma increased expression of interleukin 6 (IL-6) mRNA was found in the myxoma tissue by polymerase chain reaction (PCR) and in situ hybridisation. These cases suggest that IL-6 is overproduced in the myxoma tissue and secreted into the systemic circulatory system. This might contribute to the systemic inflammatory or autoimmune manifestations seen in cardiac myxoma. This study also showed the usefulness of PCR and in situ hybridisation for the evaluation of mRNA expression in small samples of tissue.