One hundred thirteen children referred for chronic constipation were examined by means of diagnostic work-up including anal inspection, rectal exploration, weekly bowel frequency evaluation, measurement of total and segmental intestinal transit times (TITT, SITT), contrast enema, anorectal manometry (ARM), suction rectal biopsy for histochemistry. Final diagnosis were: chronic functional "simple" constipation in 53 children; chronic functional constipation and soiling in 32; Hirschsprung's disease in 18. In 10 children, initially referred for constipation, TITT was in the normal range so they underwent no further examination. Conclusions are that bowel frequency identifies a real gastrointestinal problem, but definite diagnosis of constipation is relied on TITT. In the assessment of chronic constipation nature, ARM is more sensitive than radiology. Suction rectal biopsy is reliable in detection of aganglionosis: its accuracy can be improved by histochemical or biochemical determination of Acetylcholinoesterase.