The &bgr; dependence of the collisionless tearing instability at the dayside magnetopause current sheet is investigated analytically for various current sheet models, where &bgr; is the ratio of plasma pressure to magnetic pressure. In the present models the magnetosheath field (Bs) is separated from the magnetospheric field (Bm) by a current sheet with an antiparallel magnetic field component in the z direction and a common guiding magnetic field component (By) in the y direction. Four different current sheet models are considered. For a symmetric current sheet with equal magnetic field strength (‖Bm‖=‖Bs‖) and plasma density on its two sides and By=0 (case A), it is found that the collisionless tearing instability has a strong &bgr; dependence. An increase in &bgr; leads to a significant decrease in the tearing growth rate. For an asymmetric current sheet with fixed ‖Bm‖ and &bgr;m on the magnetospheric side and By=0 (case B) or By=const≠0 (case C), it is found that the collisionless tearing growth rate is not very sensitive to the values of &bgr;s, where &bgr;s is the ratio of plasma pressure to magnetic pressure in the magnetosheath. An increase of &bgr;s only slightly changes the tearing growth rate. For an asymmetric current sheet with fixed ‖Bm‖ and &bgr;m and a large, nonconstant By (case D), it is found that the collisionless tearing growth rate displays a strong &bgr;s dependence. The present study shows that the &bgr; dependence of the collisionless tearing instability at the dayside magnetopause is controlled by the magnetic field profile across the magnetopause current sheet. ¿ American Geophysical Union 1992