This Study addresses several questions concerning the peaking of conventional oil production from an optimist's perspective. Is the oil peak imminent? What is the range of uncertainty? What are the key determining factors'? Will a transition to unconventional oil undermine or strengthen OPEC's influence over world oil markets? These issues are explored using a model combining alternative world energy scenarios with an accounting of resource depletion and a market-based simulation of transition to unconventional oil resources. No political or environmental constraints are allowed to hinder oil production, geological constraints on the rates at which oil can be produced are not represented, and when USGS resource estimates are used, more than the mean estimate of ultimately recoverable resources is assumed to exist. The issue is framed not as a question of "running out" of conventional oil, but in terms of the timing and rate of transition from conventional to unconventional oil resources. Unconventional oil is chosen because production from Venezuela's heavy-oil fields and Canada's Athabascan oil sands is already underway on a significant scale and unconventional oil is most consistent with the existing infrastructure for producing, refining, distributing and Consuming petroleum. However, natural gas or even coal might also prove to be economical sources of liquid hydrocarbon fuels. These results indicate a high probability that production of conventional oil from outside of the Middle East region will peak, or that the rate of increase of production will become highly constrained before 2025. If world consumption of hydrocarbon fuels is to continue growing, massive development Of unconventional resources will be required. While there are grounds for pessimism and optimism, it is certainly not too soon for extensive, detailed analysis of transitions to alternative energy Sources. Published by Elsevier Ltd.