The bacterial populations of the surface layer and the centre of 15 spoiled vacuum-packed cooked ring sausages were characterized. About 95% of the total bacterial population in the surface layer and 55% at the centre were lactic acid bacteria. Another large bacterial group at the centre consisted of Bacillus spp. The lactic acid bacteria on the surface and at the centre were quite similar. Atypical streptobacteria, i.e. homofermentative psychrotrophic lactobacilli, were a major group of lactic acid bacteria in the surface layer of the spoiled sausages. Three main homofermentative groups could be observed on the basis of different carbohydrate patterns. Heterofermentative lactic acid bacteria belonged mainly to genus Leuconostoc. The proportion of leuconostocs in the spoiled sausages was also quite large. They could be divided into three main groups on the basis of different carbohydrate fermentation patterns. The lactic acid bacteria population of spoiled cooked ring sausages thus seemed to be heterogeneous. The strains isolated resembled strains observed by other workers in meat and meat products.