Based on our previous finding of elevated interferon-gamma levels in the cerebrospinal fluid (CSF), but not in serum, of HTLV-I-associated myelopathy (HAM), we assayed serum and CSF levels of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) in 20 HAM. GM-CSF and IL-1 also increased only in the CSF in 75% and 35%, respectively, of 20 HAM. TNF-alpha was not detected in any of the sera and CSFs. Multiple cytokines may be produced in the central nervous system and play an important role in HAM.