Objective. To investigate how the use of incremental and evolutionary development models affects the accuracy and bias of effort and schedule estimates of software projects. Rationale. Advocates of incremental and evolutionary development models often claim that use of these models results in improved estimation accuracy. Design of study. We conducted an in-depth survey, where information was collected through structured interviews with 22 software project managers in 10 different companies. We collected and analyzed information about estimation approach, effort estimation accuracy and bias, schedule estimation accuracy and bias, completeness of delivered functionality and other estimation related information. Results. We found no impact from the development model on the estimation approach. However, we found that incremental and evolutionary projects were less prone to effort overruns. The degree of delivered functionality and schedule estimation accuracy, on the other hand, were seemingly independent of development model. Conclusion. The use of incremental and evolutionary development models may reduce the chance of effort overruns.