This paper deals with quality from the perspective of structure, processes and indicators in surgery. In this specialty, there is a close relationship between effectiveness and quality. We review the definition and classification of surgical complications as an objective means of assessing quality. The great diversity of definitions and risk assessments of surgical complications hampered the comparisons of different surgical centers or the evaluation of a single center along time. We discuss the different factors associated with surgical risk and some of the predictive systems for complications and mortality. At the present time, standarized definitions and comparisons are carried out correcting for risk factors. Thus, indicators of mortality, complications, hospitalization length, postoperative quality of life and costs become comparable between different groups. The volume of procedures of a determinate center or surgeon as a quality indicator is emphasized.