<p>An optical disc which has a rewritable first recording region and a read-only second recording region. The first recording region has first tracks which are composed of group tracks and land tracks which are alternately provided on a disc substrate spirally or concentrically. Each first track is divided into a plurality of first sectors. Each first sector has a first header region where identification data by which the first sector is identified are recorded and a first data region in which user data are recorded with recording marks where the optical characteristics of the recording surface are changed. The second recording region has second tracks which are composed of a physical pit row which are provided on the disc substrate spirally or concentrically. Each second track is divided into a plurality of second sectors. Each second sector has a second header region where identification data by which the second sector is identified are recorded and a second data region in which read-only data are recorded by means of the pit row. The first header region includes a first physical pit row. Each pit of the first pit row has a width in a radial direction of the disc which is substantially equal to the width of the group track and, further, the pits are staggered along the center line of the group track radially with pitches of approximately a quarter of the pitch of the group track. The second header region includes a second physical pit row. Each pit of the second pit row has a width in a radial direction of the disc which is smaller than the width of the group track and, further, the pits are arranged generally along the center line of the second track to be tracked.</p>
