A case of pyogenic arthritis associated to an Actinomyces pyogenes infection in a chamois (Rupicapra pyrenaica) is described. The animal was a 5-year-old female that had been seen alone in a wooded area close to a small town in November 1995, and was lame on one front limb. One month later, it was seen again in a nearby area. Its lameness had worsened and it knuckled on both front limbs while eating. Its nutrition status had worsened considerably. On 8 January 1996 the animal was found dead. It was cachectic, its metatarsal/metacarpal-digital joints were all swollen and its hoofs were longer than normal. The microbiological study of the samples obtained showed a large number of beta-haemolytic colonies subsequently identified as Actinomyces pyogenes. Obligate anaerobic bacteria were not isolated from the samples.