This study involved analysing the carbon-13 isotope ratio (d13C) of cellulose, lignin, and whole wood powder of Balanites aegyptiaca to determine the optimal substrate for future ecophysiological studies. From seven different trees (i.e., three from the Sudanian zone and four from the Chadian Sahelian zone), 21 samples were taken for this study. Identical variation trends were observed with cellulose, lignin, and whole wood powder, with d13C values for cellulose always higher than for the other substrates, although the trees were located under different climatic conditions. The means obtained were -26.0¿‰, -28.7¿‰, and -27.1¿‰, for cellulose, lignin, and whole wood powder, respectively. Spearman's correlation test, which was used to analyse relationships between the results, revealed a strong correlation (r2 = 0.93) between the d13C cellulose values and those of whole wood powder from B. aegyptiaca, as well as between the d13C cellulose values and those of lignin (r2 = 0.73). This strong correlation between cellulose and wood powder results, and between cellulose and lignin, suggests that the isolation of cellulose is not necessary for d13C analysis of B. aegyptiaca wood.