Agile development methods have been employed across the software industry. However, it is not always clear if the used methods actually help the software firms in being more agile and if agility has a positive influence in the software firm performance. Studying these questions may turn out impossible since good measurements for assessing the overall agility of software firms do not yet exist. A need is therefore detected to measure the differences in agility between firms and finding the means to evaluate the differences in agility in reliable manner. This article examines how to measure the agility of a software firm and reports initial steps in the process of developing measurement instruments. The measurement instrument is tested against data collected from Finnish software firms and purified for further analyses.