4. Nyströ m K. Incidence and prevalence of endemic benign (epidemic) neprho-pathy in AC county, Sweden, in relation to population density and prevalence of small rodents. Acta Med Scand 1977; suppl. 609: 1-92. investigated more than six months after the acute disease still had an antibody titre of 80 or more. In 1 patient no antibodies were detected in the first serum, taken on the fourth day of symptoms. In all the others the first serum was taken on days 5-12. This early presence of antibodies accords with the find-ings of Lee et al. The antibody titres recorded with our spot slide method are of the same order of magnitude as those recorded with the lung section method. I. 2