In addition to the geological investigations presented in Part I (Delvaux et al., this volume), fluid and gas samples were taken for reservoir characterization and hydrological assessment of (at least two) geothermal systems in Mbeya area, SW Tanzania, i.e. the Northern Ngozi-Songwe and the Southern Kiejo-Mbaka system. Sampled fluids included cold surface waters as well as hot springs which were analyzed for chemical and isotopic composition. Gas samples were taken from a CO2 producing well and from bubbling cold and hot springs which were also analyzed chemically and isotopically. Additionally, free gas phases were sampled using the copper tube technique for noble gas analyses. The integrated data set of the Northern Ngozi-Songwe system including geophysical measurements (Part III: Kalberkamp et al., this volume) resulted in a conceptual model which allows siting of exploration wells for proving the predicted reservoir in the subsurface.