Electron micrographs of guinea-pig oesophageal striated muscle have been subjected to quantitative assessment. The results show that whereas the motor end-plates are considerably simpler than those of control hindlimb muscles, the Z-line width and M-line bridges are those of fast-twitch, oxidative and glycolytic fibres. Guinea-pig oesophageal striated muscle continues to defy classification into the normally accepted subtypes for skeletal muscle and should thus be considered as an example of 'visceral striated muscle'.