Ochratoxin A (OTA) is a mycotoxin frequently found in human blood and milksamples in the colder climatic zones. In addition to dietary intake, exposure may occur by inhalationof toxin containing fungal conidia. The purpose of this work was to investigate the level of OTA in bloodsamples from farm workers and non-farm working controls, and to examine if serum levels of OTA were relatedto inhalatory exposure to conidia of Penicillium verrucosum, the main OTA producer in temperate climates.Blood samples from 210 participants were analysed for the presence of OTA and IgG antibodies againstP. verrucosum conidia. The concentration of OTA was determined by HPLC (DL 10 ng/l), and the IgG levelwas determined by ELISA. All serum samples contained OTA (mean 397 ng/l, range 21-5534 ng/l). The OTAlevel in serum was unrelated to farm working, gender, age, and IgG level. The mean IgG level was significantlyhigher among farm workers than controls. Farm working, or increased inhalatory exposure to P. verrucosum,was not related to higher OTA serum levels. Inhalatory exposure to OTA from farm working seems to beof minor importance compared to dietary intake.