Lake Maggiore was studied since the beginning of last century although not systematically. Regular research started by the foundation in 1938 of the Italian Institute of Hydrobiology "Dr. Marco De Marchi" located in Verbania Pallanza. A limnographic (level and temperature profile) and weather station came into operation in 1952. Studies on plankton and on hydrochemistry of Lake Maggiore continued between the 1950s and the 1970s, showing the progressive eutrophication of the lake. Thanks also to the research of the institute, in the 1980s effective actions to control the eutrophication were undertaken, with the large-scale activation of waste water treatment plants. In the same period a program, still active, of systematic monitoring and research sponsored by the CIPAIS (International Commission for the Protection of the Italian Swiss Waters) started: it allowed collecting an uninterrupted and long-time series, with high sampling frequency, of data related to meteorology, hydrology, physic and chemistry of the lake, organic carbon and bacterial populations, phyto-and zooplankton. The analysis of these time series highlighted an oligotrophication process leading to the current state of oligotrophy of Lake Maggiore. Recent studies also showed the effects of global warming on Lake Maggiore, which went towards the gradual warming of deep hypolimnion as well as the raising of the average temperature of the surface layers.