Bond can play an important role in the assessment of existing structures, particularly when corrosion of reinforcement is to be expected. The results of bond tests on corroded bars embedded in concrete are not yet fully conclusive for the definition of bond degradation due to the effect of corroded reinforcement. The structural effects of bond degradation can assume a different importance following the resisting mechanism that is activated within the structure. A critical review of the data available is presented here; some aspects such as embedment length, corrosion rate and type of test are analysed.