The objective of this study is to investigate the dynamics within merger waves. For a sample of 1025 bids that occur in 18 industry merger waves, we measure how the returns to bidders and rivals change, as a wave is ongoing. In the first half of a wave, bidders (rivals) experience an average abnormal return of 1.5562% (0.3124%), however at late wave stages the return decreases to -1.1079% (-0.1244%). This wave effect is robust across subsamples of bids and holds in regressions that use different variables to capture the effect and control for bidder and deal characteristics.