Englacial caves observed by speleologists. The speleological investigation of moulins, intraglacial conduits and subglacial tunnels allows to collect informations which help better to understand the behavior of the glacier in movement. To find these field data it is necessary at first to conceive how appear and evolve intra-and subglacial cavities. They consist of four types : 1) those opened by meltwater ; 2) properly so called crevasses ; 3) cavities of volcanic origin ; 4) cavities in the lee of bedrock bumps. Directly observable data by the cavers must be always propped up with the time. They concern : 1) the location of cavities and their zone of drainage ; 2) the morphology of accessible entrances ; 3) the state and the stress of the ice host of cavities ; 4) an informed morphometry of investigated voids ; 5) level variations and relative age of the trapped waters, and present solid load, the nature and its disposal if necessary. All these data should be represented on plans, profits and cross sections that usually draw up the cavers. Because these documents are easely conveyed and available for consultation by a widened scientific community.