A 14-year-old boy with tubulointerstitial nephritis and uveitis (TINU syndrome) is described. Nephropathy improved without systemic cortisone treatment, whereas uveitis relapsed and was treated with topical steroids. Blood cell immunological analysis and serum analysis revealed signs of cytotoxic T-cell, macrophage and granulocyte activation, which declined as the clinical symptoms improved. This may be interpreted as an indication of their significance as markers in the pathogenesis of this syndrome or as part of a microbial-triggered immune response.