Expressions for the probability of coincidence between pairs of pulse trains are examined. The application to systems of interest in the field of electronic warfare is emphasized. Theoretical results for the limit of uncorrelated pulse trains are reviewed and new theory is developed to cover the case of coincidence between uniform pulse trains where the coincidence phenomena may be highly correlated. Monte Carlo experiments show that increasing the jitter level on one of the pulse trains causes a transition between the correlated and uncorrelated regimes.