Description:This report examines the effects on bond strength of the varying degrees of initial rusting of reinforcing bars. A survey of users’ opinions of the acceptable extent of rusting and the necessity of wire-brush cleaning was made and considerable discrepancy in users’ opinions was discovered. Bond strength tests were performed on samples re-classified by the researchers to conform to consistent criteria of rusting. The report concludes that bond strength is not impaired, and that for plain round bars the bond strength increases with an increase in the degree of rusting. An Appendix details the bond stress v slip curves for all samples in the bond tests.