This single case study describes the successful application of pelvic floor exercise to the treatment of childhood encopresis. A 10-year-old boy with lifelong incontinence of faeces and anal sphincter hypotonia practised daily pelvic floor contractions by interrupting his urine flow mid-stream, the rationale for the regime being strengthening of the sphincter muscle and improvement of its voluntary operation. Benefits to bowel control were immediate and complete cleanliness was achieved in 9 weeks. Being non-intrusive, the exercise procedure may be more acceptable to some patients with anal sphincter flaccidity than balloon biofeedback. The likely mechanism underlying the method is simultaneous contraction of the anorectal sphincter when the bladder sphincter is tensed.