Chronic viral infections in rheumatic patients are a diagnostic and therapeutic challenge. Some of the disease-modifying antirheumatic drugs (DMARD) commonly used in rheumatoid arthritis, such as methotrexate and leflunomide, are hepatotoxic. With biological therapy, which is now widely used in patients refractory to these and other DMARD, some cases of reactivation of hepatitis聽B, even fulminant cases, have been reported, especially when employing TNF antagonists and rituximab, so their use must be carefully assessed and usually accompanied by antiviral therapy. However, there have not been reports of reactivation of hepatitis聽C after immunosuppressive therapy. In patients with HIV infection, administration of immunosuppressive therapy carries a high risk of opportunistic infections, although the new highly active antiviral therapy allows the use of some drugs in selected cases.