Abstract Drilling of steam wells differs from any other drilling operation, because of particular environmental conditions and of different technical requirements. All this necessarily implies difficulties likely to bring about the failures and breakdowns dealt with in this paper. We will accordingly describe troubles most frequently occurring in steam well drillings and operations resorted to for drillings to be resumed. 1. 1. The geological nature of terrains, diameters of boreholes and environmental conditions impose extremely heavy stresses on the drilling string. Under such conditions the failure of the drilling string is not an exceptional event; we will set forth the typical aspects of such failures, studies carried out and solutions proposed up to this time. 2. 2. In lost-return water or in mud drilling at high temperature, a breakdown of the hydraulic system may cause the drill pipe in the well to be stuck. This particularly serious trouble is counteracted and solved in various ways, depending on the specific occurrence: by means of oil lubrication, strains and torsional stresses on drill pipe and resorting to the left-hand drill pipe for the subsequent screwing out and fishing of the drilling string. 3. 3. Casing job represents an important moment in well drilling, because of difficulties related with setting, cementation and maintenance of casing itself. This paper will briefly survey recorded failures from the statistical and technical points of view. Description will be centred upon possible restoring jobs, studies conducted and solutions advanced, and some recommendations will be made concerning the use of casings exposed to thermal stresses.