OBJECTIVE To test the shear bond strengths obtained when orthodontic brackets were bonded ex vivo using a composite resin and a compomer orthodontic adhesive. METHODS Specimens were tested in a special jig made to fit an Instron testing machine. After debonding, the adhesive remaining on bracket bases and enamel surfaces was mapped. RESULTS Bond strengths ranged from 8 to 23 MPa with the composite resin producing higher strengths than the compomer for similar combinations of variables. Bond strength was increased by longer curing and a longer debond interval and was higher for brackets with mesh bases than undercut bases. More compomer remained on the enamel surface after debonding than did the composite resin. CONCLUSIONS The compomer produced bond strengths within the range considered to be clinically acceptable in other studies. If it was clinically successful as an orthodontic adhesive a compomer would confer the advantage that fluoride release would help to minimize the onset of early caries around bonded brackets.