Emphasis toward manufacturability of thin film SOI devices has prompted more attention on partially depleted devices [1], [2], In this paper, drain current transients in partially depleted SOI devices due to floating-body effect are investigated quantitatively, An one-dimensional analytical model is developed to predict the transient effect and MEDICI simulation is performed to confirm the model. With the model, the amount of the turn-on current enhancement and the turn-off current suppression are calculated, The transient characteristics can be used in investigating the quality of the SOI materials by determining the carrier lifetime. The impact of the transient effect on the device parameter extraction is described.