Two stocks of shoots growing in vitro, obtained from either seedlings or adult plants, were used to study the effects of material origin, the number of previous subcultures on the establishment medium, the explant type, and the macronutrients on shoot multiplication and elongation in Myrtus communis L., always in the presence of 4.4. μM benzyladenine (BA). Shoot proliferation was influenced mainly by stock origin, with higher responses from the adult material than from the seedling material, and by the number of subcultures, with the largest rates of multiplication and elongation in the first subculture. In the first subculture, the adult material was characterized by high rates of shoot multiplication and shoot elongation, and some shoots were hyperhydric. On the other hand, in the first subculture the seedling material was characterized by lower rates of shoot multiplication and elongation, and some shoots were affected by apical necrosis. In the third and the fifth subcultures, shoot multiplication and elongation declined in both materials, and hyperhydricity or apical necrosis were never found, although higher multiplication and elongation were consistently found for the adult material. The influence of the studied sources of variation is discussed in relation to shoot multiplication and elongation.