Abstract: The preparation, stability and behaviour of b,b,b-trichloro-tert.-butyl (Tcb) esters towards various conditions of deprotection were evaluated. Tcb esters can be prepared from the halide of the corresponding carboxylic acid and b,b,b-trichloro-tert.-butanol in the presence of anhydrous zinc chloride. They are stable in acidic and basic medium and can be cleaved under mild conditions (e.g. with zinc, cadmium or indium under slightly acidic or neutral pH, with the supernucleophile cobalt(I) phthalocyanine, Table 1). Provided that the requested acyl halides are easily available, the Tcb group can be efficiently used for the protection of carboxyl functionality.