Geothermal measurements in two 100-m-deep underwater boreholes in Baikal (52 degrees 31'05" N, 106 degrees 09'11" E) yielded a thermal gradient of 41 mK/m and average heat flow of 73 mW/m(2). These values are different from earlier shallow measurements. The downhole temperature taken at depths 0, 28, 58, and 88 m sub-bottom showed an increase with a depth from 3.41 to 7.19 degrees-C. Thermal conductivity determined by needle probe on 109 samples immediately after the core recovery tends to be lower than that measured on 553 samples several weeks later in the laboratory (1.16 against 1.76 W/mK). The systematic difference of about 30% between the two methods may be due to the effect of outgassing and consolidation of sediments. A sound resolution of the questions encountered can be obtained by repeated measurements in underwater boreholes to be drilled in 1995-1997.