From 1992 to 1995, dead seabirds found on Belgian beaches were collected and various tissues of 241 birds were sampled for histopathological, bacteriological, parasitological, and toxicological investigations. The most common species examined was the guillemot ( Uria aalge ). Necropsies revealed cachexia (severe emaciation), acute haemorrhagic gastro-enteropathy and oil contamination in many of these birds. Statistical analyses were performed in order to explore correlations of these with biological parameters such as age, sex, and origin (pelagic or non-pelagic). The pelagic origin of seabirds were associated with the three main findings. Oil contamination was associated with acute gastro-enteropathy and cachexia, and cachexia was more prevalent among juveniles. Finally, cachexia and acute gastro-enteropathy were strongly associated. It is possible that oiled pelagic seabirds become cachectic and die of acute gastro-enteropathy.