Androstenone and Skatole are regarded as the main compounds leading to off odour of pork from entire males. Androstenone is one of the boar pheromones and is synthesized in the Leydig cells together with testicular hormones. Skatole is formed in the colon from the amino acid tryptophan by microorganisms. Accordingly endogenous und exogenous influences exert different effects on the formation and accretion of both substances. The present paper gives an overview about the physiological mechanisms of formation and accretion. Also interactions in the metabolism of both substances are described, which offer an explanation for elevated concentrations of both compounds in adipose tissue of boars.