Delayed milk ejection (DME), manifested most often as bimodal milk flow, occurs when the cisternal milk fraction is removed before the alveolar milk reaches the gland cistern. It is thought to be a consequence of not meeting the cows´ physiological needs due to insufficient premilking teat stimulation, inadequate timing of milking unit attachment, or both. Delayed milk ejection has been associated with decreased milking efficiency, reduced milk yield, and impaired teat and udder health. Conservative estimates suggest a loss in milk production of 7.5 kg/day in cows with DME. Most research work investigating DME in dairy cows has been conducted in cows milked with conventional milking systems. Conversely, information on DME and its possible sequelae in dairy cows milked by automated milking systems is scarce. Here, we propose to study the association of DME with milk yield in dairy cows milked by an automated milking system. We will conduct a retrospective cohort study analyzing data from 1 Canadian dairy herd using automated milking systems. We will use a general linear mixed model to study the association of DME, manifested as bimodality at the quarter level, on milk production. We hypothesize that cows that exhibit bimodality will produce less milk compared with their herd mates that show no bimodality. Testing this hypothesis is of great importance to the dairy industry, because results from this study will allow dairy producers to establish best milking practices for cows milked by automated milking systems.