AIM:To compare the demographic and clinical features of different manometric subsets of ineffective oesophageal motility(IOM;defined as ≥ 30% wet swallows with distal contractile amplitude < 30 mmHg) ,and to determine whether the prevalence of gastro-oesophageal reflux differs between IOM subsets. METHODS:Clinical characteristics of manometric subsets were determined in 100 IOM patients(73 female,median age 58 years) and compared to those of 100 age-and gender-matched patient controls with oesophageal symptoms,but normal manometry. Supine oesophageal manometry was performed with an eight-channel DentSleeve water-perfused catheter,and an ambulatory pH study assessed gastro-oesophageal reflux. RESULTS:Patients in the IOM subset featuring a majority of low-amplitude simultaneous contractions(LASC) experienced less heartburn(prevalence 26%) ,but more dysphagia(57%) than those in the IOM subset featuring low-amplitude propagated contractions(LAP;heartburn 70%,dysphagia 24%;both P ≤ 0.01) . LASC patients also experienced less heartburn and more dysphagia than patient controls(heartburn 68%,dysphagia 11%;both P < 0.001) . The prevalence of heartburn and dysphagia in IOM patients featuring a majority of non-transmitted sequences(NT) was 54%(P = 0.04 vs LASC) and 36%(P < 0.01 vs controls) ,respectively. No differences inage and gender distribution,chest pain prevalence,acid exposure time(AET) and symptom/reflux association existed between IOM subsets,or between subsets and controls. CONCLUSION:IOM patients with LASC exhibit a different symptom profile to those with LAP,but do not differ in gastro-oesophageal reflux prevalence. These findings raise the possibility of different pathophysiological mechanisms in IOM subsets,which warrants further investigation. AIM: To compare the demographic and clinical features of different manometric subsets of ineffective oesophageal motility (IOM; defined as ≥ 30% wet swallows with distal contractile amplitude <30 mmHg), and to determine whether the prevalence of gastro-oesophageal reflux Unique between IOM METHODS: Clinical characteristics of manometric subsets were determined in 100 IOM patients (73 female, median age 58 years) and compared to those of 100 age-and gender-matched patient controls with oesophageal symptoms, but normal manometry. Supine oesophageal manometry was RESULTS: Patients in the IOM subset featuring a majority of low-amplitude simultaneous contractions (LASC) experienced less heartburn (prevalence 26%) performed with an eight-channel DentSleeve water-perfused catheter, and an ambulatory pH study assessed by gastro-oesophageal reflux. , but more dysphagia (57%) than those in the IOM subset featuring low-amplitude propagated contractions (LAP; heartburn 70%, dysphagia 24%; both P ≦ 0.01 LASC patients also experienced less heartburn and more dysphagia than patient controls (heartburn 68%, dysphagia 11%; both P <0.001). The prevalence of heartburn and dysphagia in IOM patients featuring a majority of non-transmitted sequences (NT) was No differences inage and gender distribution, chest pain prevalence, acid exposure time (AET) and symptom / reflux association existed between IOM subsets, or Between subsets and controls. CONCLUSION: IOM patients with LASC exhibit a different symptom profile to those with LAP, but do not differ in gastro-oesophageal reflux prevalence. These findings raise the possibility of different pathophysiological mechanisms in IOM subsets, which warrants further investigation.