Vector data is captured using various methods, e.g. manual digitizing, automatic vectorization etc. Errors or inconsistencies, e.g. self-cutting polygons, identical points etc, can not be avoided, even if digitizing is done very carefully. Vector data must be analyzed and corrected prior to any GIS application. This process is called "line-cleaning". In this paper we introduce a computer program that is capable of analyzing of building objects. It can correct digitizing errors and improve geometric quality of data, doing right angle adjustment, making buildings parallel to streets etc. The program was designed to process building objects before generalization with CHANGE generalization software package. However, it can also be used independently. © 2004 International Society for Photogrammetry and Remote Sensing. All rights reserved.