It appears to be widely accepted in the real options literature that an increase in uncertainty should have an inhibiting effect on investment. Our article demonstrates that the notion of a negative uncertainty-investment relationship is not always correct. We show that in certain situations, an increase in uncertainty can actually increase the probability of investing, and thereby have a positive impact on investment. (C) 2000 Elsevier Science B.V. All rights reserved. JEL classification: C6; E2.