The aminoacid excretion levels of 59 normal and 75 physically and/or mentally handicapped children were measured with ion-exchange chromatography. A computer-assisted statistical analysis of the results from the normal population was used to calculate an approximating frequency distribution. 18 patients were found to be excreting one or more aminoacids above the normal 99.75th or 100th percentiles. They included 1 with dibasic aminoaciduria; 1 six-year-old with phenylketonuria; 1 with hyperphenylalaninuria; 5 with cystathioninuria; 2 with hyperglycinuria; 1 with hyperglycinuria and hypertaurinuria; 5 with hypertaurinuria; 1 excreting high levels of taurine, serine, tyrosine, and histidine, and 1 with asparaginuria.