Regular 3 cycles per minute (cpm) gastric myoelectrical activity (GME) is recorded in healthy adults and children older than 6 months. Our previous study indicated an absence of the regular 3 cpm waves in newborns. The aim of this study was to investigate the developmental change of GME in newborns.Methods: The study was performed in 4 preterm infants (mean gestation age at birth: 33 weeks) at the birth age of one week and one month. GME was recorded by placing 3 electrodes on the abdomen, a technique called electrogastrography (EGG). The EGG recording was made for a continuous period of 12 hours, from 9 p.m. to 9 a.m., using an ambulatory EGG recorder(Synectics Medical, Irving, TX). The EGG data were analyzed using the spectral analysis method after the deletion of recording periods contaminated by motion artifacts. The percentage of normal GME was assessed by computing the percentage of time during which 2-4 cpm waves were found in the power spectrum of the EGG. Results: The percentage of normal GME increased from 31.2 ± 5.7% at one week to 56.1 ± 11.3% at one month. Gastric arrhythmia (no rhythmic waves) dominated the recording in three of the four subjects at one week but remarkably decreased at one month (38.4 ± 8.9% vs 24.5 ± 6.3%). Tachygastria at about 6 cpm was found in the other infant at one week and changed to a normal rhythm of 3.5 cpm at one month.Conclusion: These data suggest that there is a maturing process of GME in preterm newborns. Further studies are being undertaken in more subjects to investigate the effects of gestation age, birth age, and feeding methods on the maturation of GME.