Maritae of family Notocotylidae have no ventral sucker, an organ that serves for attachment in many other digeneans. Instead, attachment is accomplished through the ventral concavity which is formed by the whole body. Musculature providing such an attachment was previously described only in part, and specific patterns of body-wall and internal muscle arrangement in notocotylids have never been studied before. In this paper we describe muscle system organization in maritae of three notocotylid species by means of fluorescent actin staining and confocal microscopy. A very special U-shaped pattern of body-wall longitudinal muscle fibres is found to support the ventral concavity. Together with very prominent dorsoventral musculature this pattern must play a key role in actions of ventral concavity. Other details concerning the muscle system are provided, including the musculature of ventral protrusions, oral sucker, walls of digestive tract and reproductive organs. We discuss functionality of the musculature and