Sera collected from 507 hunter-killed wild pigs (Sus scrofa) between 1993 and 2004 from five geographic regions in northern Spain and seven regions in southern Spain were assayed for antibodies to Toxoplasma gondii by the modified agglutination test (MAT). Antibodies to T. gondii were detected in 185 (38.4%) of 507 pigs with titers of 1:25 in 71, 1:50 in 111 and > or =1:500 in 3; seroprevalence was significantly higher (P<0.05) in pigs from southern regions. Seroprevalence was density dependent; it was higher in pigs from high stocking per hectare and availability of forage. Statistically significant differences were not observed between T. gondii seroprevalence and hunting estates (open versus fenced), sex or age. Serological results indicate a widespread exposure to T. gondii among Spanish wild boars, suggesting that this population could represent a public health risk for persons that handle or consume raw or undercooked infected wild pig meat.