Background: Rumination syndrome is characterized by recurrent regurgitation of recently ingested food into the mouth. Differentiation with other diagnoses and gastroesophageal reflux disease (GERD) in particular, is difficult. Recently, objective pH-impedance (pH-MII) and manometry criteria were proposed for adults. The aim of this study was to determine diagnostic ambulatory pH-MII and manometry criteria for rumination syndrome in children. Methods: Clinical data and 24-hour pH-MII and manometry recordings of children with a clinical suspicion of rumination syndrome were reviewed. Recordings were analyzed for retrograde bolus flow extending into the proximal esophagus. Peak gastric and intraesophageal pressures closely related to these events were recorded and checked for a pattern compatible with rumination. Events were classified into primary, secondary, and supragastric belch–associated rumination. Key Results: Twenty-five consecutive patients (11 males, median age 13.3 years [IQR 5.9-15.8]) were included; recordings of 18 patients were suitable for analysis. Rumination events were identified in 16/18 patients, with 50% of events occurring <30 minutes postprandially. Fifteen of 16 patients showed ≥1 gastric pressure peak >30 mmHg, while only 50% of all events was characterized by peaks >30 mmHg and an additional 20% by peaks >25 mmHg. Four patients had evidence of acid GERD, all showing secondary rumination. Conclusions and Inferences: Combined 24-hour pH-MII and manometry can be used to diagnose rumination syndrome in children and to distinguish it from GERD. Rumination patterns in children are similar compared with adults, albeit with lower gastric pressure increase. We propose a diagnostic cutoff for gastric pressure increase >25 mmHg associated with retrograde bolus flow into the proximal esophagus.