Evolutionary software development processes mainly address concerns regarding client requirements and risk management. A side-effect of allowing frequent, and often unanticipated, modifications to the software is that they may result in poor structure, because the designers may not have anticipated the final set of requirements that would be implemented. By monitoring structural properties of the software one may be able to identify and correct design problems before they become unmanageable. Ways in which degradations in structural properties of the software can be measured are described and empirically validated, based on data collected from an industrial Java development project. The measures are validated by using them as candidate variables in a prediction model of the actual effort required to make modifications to the evolving software system. The results suggest that some measures that combine existing structural attribute measures with a weighting factor based on the relative proportion of change in each class are reasonably accurate predictors of change effort. This constitutes initial, empirical evidence that the proposed measures are valid quality indicators. Consequently, they may help designers to identify and correct design problems during the evolutionary development of object-oriented software.