Abstract. This paper presents the effect of 'schedule compression' on software project management effort using COCOMO II (Constructive Cost Model II), considering projects which require more than 25 percent of compression in their schedule. At present, COCOMO II provides a cost driver for applying the effect of schedule compression or expansion on project effort. Its maximum allowed compression is 25 percent due to its exponential effect on effort. This research study is based on 15 industry projects and consists of two parts. In first part, the Compression Ratio (CR) is calculated using actual and estimated project schedules. CR is the schedule compression percentage that was applied in actual which is compared with rated schedule compression percentage to find schedule estimation accuracy. In the second part, a new rating level is derived to cover projects which provide schedule compression higher than 25 percent.