■ In this paper, we draw attention to the interaction between the number of partners and the direct competition between these when explaining the longevity of stakes in joint ventures (JVs). ■ We argue that increases in the number of partners have a positive effect on the longevity of stakes in JVs only when all of these are competitors, especially if the JV includes marketing activities. In contrast, if not all of the partners are competitors, the effect of the number of partners will be the opposite. Our hypotheses are empirically tested via several estimates of proportional hazard regressions, using a sample of JVs carried out by Spanish firms. © Gabler Verlag 2006.