Mud boils, classified as non-sorted circles, are a common patterned ground phenomenon of permafrost areas. They typically consist of a bare circle center of cryoturbated soil and are surrounded by vegetation on more stable soil. The objectives are to examine differences in seasonal hydrologic and thermal dynamic across this gradient of cryoturbation, i.e. the region below the organic border and the mud center. We installed instruments in a mud boil at a site close to Ny-@lesund, Spitsbergen, in September 1998. The bare soil circle center ranges about 1 m in diameter and is surrounded by a vegetated border consisting of a mixture of low vascular plants, mosses and lichens. Fine soil (>95% clay and silt) in the lower part of the profile is overlain by coarser grained material (silt and sand). The grain size distribution also suggests an upwelling of fine material in the center of the circle. Temperature and moisture sensors were installed over a vertical 1 m×1 m profile and hourly data recording started in September 1998. Surface irregularities, as well as variations of grain size and moisture, create a non-uniform thermal and hydrologic dynamic. We qualitatively analyze this dynamic with respect to the mud boils physical stability.