The ideal conditions for the determination of silicon by graphite-furnace atomic absorption spectrometry have been investigated by using high-temperature equilibrium calculations. All reasonable reaction products resulting from the reaction between Si, C, O, H, S, N, Ar and Na have been considered. The results show that SiO 2(s) is the stable silicon compound for temperatures below 1500 K. For higher temperatures Si 3N 4(s), SiC(s), SiO(g), SiO 2(s), Si(g), SiN(g), SiCl 2(g) and SiS(g) are the main silicon-containing reaction products. SiO(g) is always formed in the interval 1600–2200 K independently of the partial pressure of oxygen. The basic requirement for the quantitative formation of silicon atoms at 2600 K is that the partial pressure of atomic oxygen is less than 10 -12atm. The main condition for the formation of silicon carbide is an extremely low partial pressure of oxygen. Losses of silicon by the formation of SiO(g) during heating of the graphite tube were experimentally shown to be reduced by using isothermal atomization. An equilibrium model for the formation of silicon atoms is discussed. This model takes into consideration the decrease in the partial pressure of oxygen during the atomization step. The results obtained show that silicon atoms are formed from SiO(g) at the temperatures pertaining to the beginning of the atomization cycle and from SiC(s) at somewhat higher temperatures.