This paper studies idiosyncratic risk of new ventures. An option-based model of a new venture with multistage investments and jumps is developed. Our model ex- plains (1) why new ventures?idiosyncratic volatility eventually decreases as they clear R&D investment stages and become mature ?rms ?the stage-clearing e¤ect; (2) the negative relation between jumps in value and subsequent idiosyncratic volatility ?the jump e¤ect; (3) the dynamics of idiosyncratic volatility under di¤erent schedules of staged venture capital investments; and (4) the e¤ect of di¤erent schedules of staged investments on ?rm valuation with the presence of jumps. Empirically, we develop a generalized Markov-Switching EARCH model to simultaneously capture structural changes in ?rms?idiosyncratic volatility and the relation between jumps and idiosyn- cratic volatility. Using a hand-collected dataset of early-stage biotech ?rms, we ?nd empirical evidence supporting the jump e¤ect and the stage-clearing e¤ect described by our model.