The aim of this study was to compare the validity, reliability, and time needed to use the Eismann index, the Eismann-Farcnik (EF) index, and the index of orthodontic treatment need (IOTN).One hundred pretreatment study casts of adolescent patients in the permanent dentition period (mean age, 15.4 years; SD, 0.4 year; 53 girls, 47 boys) were used. Three examiners trained and calibrated in the use of the Eismann and EF indexes and the IOTN scored the casts using the 3 indexes. A panel of 10 orthodontists individually rated the same casts for degree of malocclusion severity. The mean rating of the panel on the severity of malocclusion was used as the gold standard for evaluating the validity of the 3 indexes. Furthermore, the agreement of the 3 indexes in assessing the severity of malocclusion was evaluated. Ten randomly selected casts were reevaluated for the reliability study. Each evaluation was timed and rounded off to the nearest half minute.The intraclass correlation coefficient indicated excellent agreement of the EF index with the ratings of the orthodontists (0.819), good agreement for the Eismann index (0.742), and moderate agreement for the IOTN (0.597). Receiver operating characteristic curves were plotted for the 3 indexes. The diagnostic accuracy, as determined by the area under the curve, was found to be the best for the EF index, followed by the Eismann index and the IOTN. Intraexaminer and interexaminer reliability was high (>0.75) for all 3 indexes. The most time-consuming methods were the EF (27.10 minutes) and the Eismann (26.86 minutes) indexes; the IOTN (1.97 minutes) was the least time-consuming method.All 3 indexes are valid and reliable methods for assessing malocclusion severity. The EF index is the most time-consuming method, but it had the best agreement with clinical orthodontic diagnosis.