Temperature and velocity fields near an air-bubble in silicon-oil under a heated horizontal wall were investigated. The studies were made with silicon oils of different viscosities so that a wide range of Marangoni numbers was encountered. Schlieren interferograms were taken to analyse the temperature field. For the axisymmetric problem the Abel integral equation was solved numerically by using a coefficient procedure. From the recorded temperature distributions isotherms, radial temperature lines and the temperature along the bubble surface were determined graphically. At low Prandtl- and high Marangoni-numbers an oscillatory instability was observed. The flow field was investigated with neutral-buoyant light scattering glass spheres by observation of the meridian plane of the bubble with a thin light-sheet. The convective mechanism of the flow was recorded photographically by taking pictures with various exposure times. Thus a qualitative and quantitative description of the flow was possible.