Experiences of making software development and purchase contracts between a user organization and several softwarevendorsareanalyzedoveradecade-longperiod. Threeinformationsystemshistoriesarepresented as case examples. The analysis is based on observations of the contract negotiations. Transaction cost frameworkisusedtoexplaintheformsofthejointorganizationalrelationsbetweentheparties. Theanalysis yields a descriptive model that depicts in a concise way how the relationships have evolved. The model identifies encounters between the vendors and the client which may change the contractual state between the parties. The passages between consecutive encounters are called episodes. By perceiving contractual systems development as a series of encounters and episodes, it is possible to identify the critical turning points of development work and to display the dynamics of contracting. The paper ends with a discussion of the findings and some implications for researchers and practitioners.