This paper explores how uncertainty in duration estimates is handled, with the subject area being new product development. In many projects simple deterministic estimates of nominal task duration may be sufficient (for several given reasons). Various methods for coping with uncertain durations are described, including PERT, fuzzy theory, and probabilistic computations (three sub-types). These are illustrated with representative data, and the benefits and disadvantages discussed. Two major risk areas with any and all stochastic estimating processes are identified as the unreliability of the estimates, and the ambiguous interpretation. Implications are: • Project managers might benefit from greater familiarity with PERT. • Software developers need to implement PERT better, and should also consider implementing fuzzy theory. • Design managers might be best to aim for adequate rather than exhaustive project plans, scope definitions and risk assessments. They might complement this by active project monitoring to give flexible, fast, efficient and effective response during deployment.