The present review covers the advances in the chemistry of 6-aryl-5-substituted- 3(2H)-pyridazinones made in our group during our search for new antiplatelet agents. As part of this project we have developed a number of different, useful synthetic pathways that have allowed the preparation of a wide range of 6-aryl-5-substituted- 3(2H)-pyridazinones. Our systematic studies on this series of compounds have led to the development of new and efficient procedures based on the use of the appropriate 5-substituted-6-phenyl-3(2H)-pyridazinones as star-ting materials in the preparation of 6-phenyl-4,5-substituted-3(2H)-pyridazinones.