Remote sensing techniques supply valuable observations from distant regions, which should not be disturbed or cannot otherwise be monitored. These observations often provide integrated information along the whole signal path. Thus, particular data analysis is necessary in order to generate a spatial mapping of the observed quantities. If a sufficiently large number of line-integrating or beam-integrating observations is available, tomographic techniques can be applied to combine these quantities to a spatially resolved two-dimensional or three-dimensional field according to output data of numerical atmospheric models. That way, for example, atmospheric temperature and wind fields can be derived by a special application of tomography presented in this chapter: acoustic travel-time tomography. This method uses the propagation speed of acoustic waves in air to estimate temperature and wind fields within the atmospheric surface layer. The basic setup for acoustic travel-time tomography is a configuration of sound sources and sound receivers that are placed around an area under investigation. Knowing their exact positions, travel-time measurements provide information on the speed of sound along the acoustic propagation path between the sources and receivers. A subsequent joint analysis of the sound wave travel times, the tomographic inversion, gives the spatially resolved temperature field and the wind field. The technical setup of the method is described together with the required calibration and quality control procedures. Furthermore, selected results and an estimate of the achieved quality are presented.