OBJECTIVE: To compare the diagnostic accuracy of contrast enema (CE), anorectal manometry (ARM), and rectal suction biopsy (RSB) for the detection of Hirschsprung's disease (HD). STUDY DESIGN: Following a prospective protocol, infants suspected of HD underwent all 3 index tests. Children with positive results on 2 or more index tests or who continued to have severe bowel problems underwent a full thickness biopsy as reference standard. Clinical follow-up was the reference standard in all other children. RESULTS: Between 2000 and 2003, 111 consecutive patients (67 boys; median age, 5.3 months) in whom HD was suspected were enrolled. HD was found in 28 patients. RSB had the highest sensitivity (93%) and specificity (100%) rates, but values were not significantly different from CE (sensitivity, 76%; specificity, 97%) or from ARM (sensitivity, 83%; specificity, 93%). Inconclusive test results occurred in 8 infants with CE, in 15 infants with ARM because of agitation, and in 2 infants with RSB. CONCLUSION: RSB is the most accurate test for diagnosing HD, and it has the lowest rate of inconclusive test results.