Early spoilage of commercial vacuum-packed chilled lamb legs was manifested as an objectionable cheesy , deep tissue odour that became evident when a cut was made into the stifle joint. Investigation of the probable causative agents led to the isolation of two psychrotrophic strains of clostridia. The isolates could not be identified using traditional identification schemes. One isolate was able to produce strong, objectionable cheesy odours in deep tissues of artificially inoculated beef.