In this study the reliability of anorectal manometry (ARMM) in Hirschsprung's disease (HD) in the neonatal period is evaluated. ARMM was performed in 59 patients (age ranging between 2 to 90 days) in whom HD was suspected. Rectal biopsy was performed in 23 newborn whose rectoanal inhibitory reflex (RAIR) was not identified in the ARMM study and in 13 RAIR-positive newborn due to strong clinical signs supporting HD or persistence of symptoms during their follow-up. Other RAIR-positive patients were followed up to 4 months to 3.5 years and no problems were encountered. Among the 36 newborn with rectal biopsies, if the results were compared to ARMM studies, there were one false-positive and two false-negative results. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of ARMM in the diagnosis of HD are 91.6%, 95.6%, 84.6% and 91.6% respectively. We conclude that ARMM can be used as a screening test in patients in whom HD is suspected during the neonatal period, but for definitive diagnosis it must be combined with other diagnostic tests.