Absence of the peristaltic contractions in the esophageal body and the failure of the lower esophageal sphincter (LES) post-deglutitive relaxation are the major motor disturbances in patients with achalasia. These alterations are usually evidenced by means of stationary esophageal manometry, which is able to record changes over a brief period. The aim of this work has been to study the circadian esophageal motor activity of the esophageal body in patients with achalasia, using a non-perfused ambulatory manometry system. Ten patients with untreated esophageal achalasia (dilatation < or = 5 cm) had a 24-hour ambulatory esophageal manometry. The portable recording system consisted of a computerized data logger and a probe with four microtransducers 5 cm apart, the distal one being positioned 5 cm above the LES. A microtransducer, positioned 1 cm below the upper esophageal sphincter, recorded the swallow activity. Contractions frequency (n/min), mean amplitude (mmHg), mean duration of contraction (sec), percentage of contraction > 7 sec, percentage of multipeaked, repetitive and isolated contractions, and percentage of peristaltic and simultaneous sequences were evaluated and analysed during the following periods: meal-time (MT); upright (UP); supine night-time (NT). On the basis of the relationship with swallows the contraction events were classified as post-deglutitive or spontaneous. The data out of a group of 65 normal subjects were used as control. Student's t-test and Wilcoxon's rank-sum test were used for statistical analysis. Peristaltic sequences were detected in all patients, 27.8 +/- 12.6% of the total, and the 19.5 +/- 11.06% of these were complete. Moreover primary peristaltic sequences were present in 33.1 +/- 23.4% of all peristaltic sequences. In contrast to current trends, our results show surprisingly the presence of peristaltic activity in patients with achalasia (27.9% MT; 26.9% UP; 28.1% NT). We believe these results are related both to the use of an ambulatory system, which allows 24-hour monitoring and to the use of microtransducers, which are able to detect motor events with great accuracy. These motor events are usually not detectable by stationary perfused systems.