Today, many organizations have focused on the issue of quality (total quality management (TQM) and ISO standards) to sustain their survivalsurvive in the market and to respond customers' needs appropriately and timely, but the success of implementation of these systems is doubtful. Public and private organizations in Bushehr and Shiraz (which have implemented the ISO systems) were chosen to identify variables affecting these systems success. After reviewing the theoretical literature, these variables are categorized into 4 segments: managerial, personnel (employees), external and cultural. Questionnaire was used to gather data. Data were analyzed using Discriminant Analysis. The results indicate that the most important ISO implementation variables are 1) continuous improvement in the organization, 2) ISO Compatibility with strategies and organizational structure, and 3) the quality of internal and external communications. Based on these results, these three variables can estimate correctly ISO implementation success levels as 80.2 percent.