A 54 km long seismic refraction profile has been measured just south of the river Indalsälven and lake Storsjön in west-central Jämtland. The profile cuts across the Caledonian front in an area where the Precambrian crystalline basement is covered by folded Lower Paleozoic sedimentary rocks belonging to the Jämtland Supergroup. The time-delay method was used in the interpretation of the travel-time data. In the final model a linear increase with depth was assumed in both the basement and its cover. The model shows that the thickness of the sedimentary cover increases from about 300 m along Storsjön in the east to a maximum of some 1800 m south of the lake Ockesjön to the west. Further westwards the thickness of the sedimentary cover again decreases to less than 300 m and the possibility exists that the basement may be allochthonous. The velocity of the uppermost basement proved to be 5.93 km/s+0.11 km/s-km.