In 73 patients with myelomeningocele (mean 17.2 years, range 5 to 40 years) the classification of level of lesion was studied according to six commonly used classification systems and to the ambulation groups of Hoffer. The distribution of the patients into classes of thoracic-level lesions was the same for four classification systems in 10 patients and for two classification systems into categories of level L3 in 14 patients. For the other patients discrepancies occurred between systems for lesions of level L3 and downward. None of the patients was consistently categorized in the functional ambulation groups of Hoffer using all classification systems. The results show that it is not possible to compare neurological lesion levels classified according to the different systems described in this study and consequently that the distribution into the functional ambulation groups of Hoffer varies. To enhance communication and facilitate comparing the results of treatment we suggest using some basic criteria for patient documentation.