Organochlorines can possibly cause toxic effects in birds. In this thesis, levels and relationships between health parameters, organochlorine contaminants (OCs) and body condition index (BCI) in black-legged kittiwakes and common eiders were assessed. Immunoglobulin Y (IgY)levels and Oxidative stress (OSI) were measured in plasma of birds, and served as health parameters. OCs were measured in pectoral muscle of birds and served as explanatory variables. In addition, BCI, as a measure of the physiological state in individual birds were examined. Variations in IgY, OSI, OCs and BCI were also assessed between years, months and two locations (Liefdefjorden and Kongsfjorden) on Svalbard. Organochlorine pesticides explained a significant amount of variation in plasma IgY in black-legged kittiwakes, while polychlorinated biphenyls explained a significant amount of variation in plasma IgY in common eiders. OSI was only explained by polychlorinated biphenyls in black-legged kittiwakes. Regarding variations in IgY, OSI, OCs and BCI between years, months and locations no clear conclusions were made. However, a pattern of no increase of bioavailable OCs were suggested for Kongsfjorden. Also, higher concentrations of some OCs were seen in Kongsfjorden compared to Liefdefjorden.