Lipocalins as biochemical markers of disease have been used extensively. The clinical indications relate to almost any field of medicine, such as inflammatory disease, cancer, lipid disorders, liver and kidney function. Some of the more well-known lipocalins that have been used as markers of disease are orosomucoid, Protein HC (alpha(1)-microglobulin), apolipoprotein D, retinol-binding protein, complement C8 gamma, prostaglandin D synthase and human tear prealbumin, and these markers will be briefly reviewed in this article. Emphasis, however, will be put on the description of another newly described lipocalin, i.e. human neutrophil lipocalin/neutrophil gelatinase-associated lipocalin (HNL/NGAL), since the body fluid measurement of HNL/NGAL was shown to be a superior means to distinguish between acute viral and bacterial infections and also to accurately reflect the activity and involvement of neutrophils in a variety of other diseases.