Previously we have observed different characteristic chromatographic ultraviolet absorbancy profiles at 280 nm for urinary protein precipitates from patients with behavioral disorders. The purpose with this study was to look for similar changes in urinary protein excretion from the grossly disabled patients with the Rett syndrome. Benzoic acid precipitates from the urine from 20 patients were chromatographed on a Sephadex G-25 gel column. There appeared 3 different profiles: 6 as observed in normal controls, 5 like that in compulsive behavior, and 9 were similar to those observed for autistiform-schizophreniform patients. The profiles did not mirror the behavioral observations for the patients, although the first group of 6 patients were the least disabled, whereas the last 9 patients were the most seriously ill. In conclusion the chromatographic profiles suggest a heterogeneous group of patients, but we need more observations for several patients over time, as there may be a change with the exacerbation of the disease.