Recently, a debate has begun concerning the relationship between conflict events over time between the same disputants. While research on rivalries and recurrent conflict suggest that crises are related over time, others (Gartzke and Simon 1999) doubt the empirical and theoretical foundations of this research. We agree with the critics that the proposition that conflicts between adversaries are related over time remains only weakly substantiated. To fill this lacuna, we test four hypotheses relating past crisis behavior and sequences to subsequent conflict, using International Crisis Behavior (ICB) project data. Our results support the serial crisis hypothesis and suggest that the probability of subsequent crises and wars increase with each past crisis. Our findings also reinforce the inclination to give more emphasis to the analysis of rivalries.