In the spectrochemical analysis of high speed steels with a small current activated a.c. arc (after Aбрамсон), the results of analysis were found to be affected by different previous heat-treatments given to the steel samples. To study this effect we selected 10 chromium steel samples of different carbon content. Spectrochemical analysis of these samples under different procedures of heat treatment shows that with an a.c. arc (5 amp.) the results of analysis of Cr for annealed and for hardened samples of the same steel are different and the difference increases with the increase of carbon content. We are inclined to think that in a low energy light source, the evaporation and the excitation of the alloying elements vary according to the existing form of carbon and this directly affects the results of spectrochemical analysis. The magnitude of this effect is different for different alloying elements, it is considerable in the case of Cr but is inappreciable in the case of Mn and Si.How to eliminate the effect of micro-structure on spectrochemical analysis was also investigated. It was found that with a low energy light source, the effect can not be eliminated by increasing the time of pre-arcing. However, this effect is considerably reduced by using a spark source or an a.c. arc source of large current.