An exceptional muscle development in some meat-producing animals is due to the increase in the number of muscle fibers (hyperplasia) or increase in their individual diameter (hypertrophy). The genetic mechanism of the former is well known. It results from mutation in the myostatin gene. The determination of muscular hypertrophy is poorly understood. In pigs this phenomenon is associated with muscular hypermetabolism and contraction induced by stress. Muscle development is controlled by genes called muscular regulatory factors. Four genes belong to this family: myogenin, myf-3, myf-5 and MRF4. While myf-3 and myf-5 are responsible for establishment and maintenance of skeletal myoblasts, myogenin and MRF4 control differentiation of myoblasts into myotubes. Their activity is influenced by other genes and physiological factors. Understanding of the mechanisms involved in myogenesis would provide a useful tool for controlling meat production in farm animals.