We evaluated urodynamically and radiologically 54 children with myelodysplasia and neurological deficits at or below the S1 level. Baseline urodynamic testing was normal in 13 patients (24%), while 12 (22%) had an upper motor neuron and 13 (24%) had a lower motor neuron type of dysfunction. A total of 7 patients (13%) had a mixed upper and lower motor neuron type, and 9 (17%) had only lower motor neuron dysfunction of the urethral sphincter with a normally contractile bladder. Followup studies varying in time from 1 month to 10 years showed a changing neurourological lesion in 29 patients (54%): 25 deteriorated while 4 improved. Of the 54 children 20 had hydronephrosis and/or vesicoureteral reflux. Incontinence was the major problem in 41 patients (75%), and was managed initially with pharmacological agents and/or clean intermittent catheterization, with 9 of the 41 eventually requiring surgery. Urodynamic assessment reveals a variable picture that does not correlate well with the apparent neurological examination. Despite the low level of the neurological deficit, many children may be at risk for urinary tract deterioration. These findings emphasize the importance of continuous surveillance and appropriate management in this group of myelodysplastic children who have the greatest potential for a normal life.