Abstract: A tissue expander implant (10) arranged to be anchored in position within a cavity formed in the body for the controlled expansion of overlying tissue. The tissue expander implant (10) comprises a first expandable envelope (18) defining a first closed chamber (18a), first inflation means for enabling the controlled inflation of the first expandable envelope with a biocompatible fluid, a second expandable envelope (20) located in side-by-side relationship with the first expandable envelope and defining a second closed chamber (20A) and second inflation means for enabling the controlled inflation of the second expandable envelope with a biocompatible fluid. The first and second expandable envelopes have a textured external surface for promoting adhesion to overlying tissue.