Purpose: The aim of this study was to compare two different methods in arm volume assessment in healthy subjects and investigate the interrater reliability of these methods. Material and methods: Twenty-four volunteer subjects participated in this study. Two raters measured each subject with circumferential measurement and with volumetric measurement (water displacement method). Volume was calculated using Frustum formula with results from circumferential measurements and was compared with volumetric measurement results. Interrater reliability for these two methods was investigated. Results: Arm volumes obtained with these methods had high interrater reliability. Correlation coefficients for volumetric measurements and volumes calculated with circumferential measurements were 0.983 and 0.998 and respectively. Arm volume calculated by Frustum model correlated strongly with volume determined by water displacement But, there was 452.67 +/- 167,22 ml difference between two methods. Conclusion: Calculated volume results and volumetric measurement results had high correlation, for this reason physiotherapist can use both methods to assess volume. But differences between the two methods show that these methods can not be used interchangeably. Thus, the same physiotherapist or different physiotherapists should use the same assessment method for Iterative measurements in a patient or study.