Different types of instrument are used all around the world to evaluate ground level solar UV erythemal doses. One difficulty when comparing measurements is to evaluate the reliability of the different experimental techniques. The purpose of this paper is to compare the erythemal doses measured by broadband, narrow band and spectral instruments, weighted by their relative UV response for different zenith angle and atmospheric conditions. Three instruments are used for this comparison: 1) a broadband UV meter (Yankee Environment System, UVB-1); 2) a narrow band four filters radiometer (Biospherical Instruments Inc., GUV 511-C) and 3) a spectro radiometer (Jobin-Yvon, modified HD-10), all of them are equipped with PTFF (Teflon ®) diffuser and measure global solar irradiance. Measurements were performed in clear sky conditions, for solar zenith angle (SZA) ranging between 80 and 30°. Comparison calculated and measured CIE doses obtained by the different techniques are presented and discussed. Some sensitivity analysis is presented in order to explain the observed discrepancies.