An in vitro preparation from the media of the pig carotid artery develops somewhat higher force/cell cross-sectional area with one-fifth the myosin content of skeletal muscle cells. The following results suggest that this performance reflects cellular properties rather than the arrangement of cells within the tissue: (1) force development at the peak of the length-force curve is independent of the length of the tissue segment in a strip of constant cross-section, and (2) average cell length is directly proportional to tissue length. We conclude that the contractile system of arterial smooth muscle cells is specialized for force generation and that the mechanical properties of the pig carotid media preparation provide valid estimates of cellular function.