Serum samples from 78 European wild boars (Sus scrofa) harvested during the 1999–2000 hunting season were tested for antibodies to Brucella spp., classical swine fever virus, Erysipelothrix rhusiopathiae, Haemophilus parasuis, Leptospira interrogans serovar pomona, Mycoplasma hyopneumoniae, pseudorabies virus (PRV), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome virus, Salmonella serogroups B, C, and D, Streptococcus suis, and swine influenza virus (SIV) serotypes H1N1 and H3N2. Samples were collected from Sierra Morena and Montes de Toledo in southcentral Spain. Antibodies were detected to PRV (36%), L. interrogans serovar pomona (12%), PPV (10%), E. rhusiopathiae (5%), SIV serotype H1N1 (4%), Salmonella serogroup B (4%), and Salmonella serogroup C (3%). Our results suggest that more research is needed to describe the epidemiology of infectious diseases of Spanish wild boars.