IL-18 is an inducer of apoptosis/tissue injury. IL-18 messenger RNA expression was examined in adipose tissue (AT) obtained from HIV patients with lipodystrophy, without lipodystrophy and healthy controls. IL-18 mRNA was expressed in AT at increased levels in lipodystrophy-positive compared with lipodystrophy-negative patients and healthy controls. Higher levels of IL-18 mRNA were found in femoral-gluteal AT compared with abdominal AT, and correlated with limb fat loss. These findings suggest that IL-18 is linked to HIV-associated lipodystrophy.