Lippia sidoides Cham. (Verbenaceae) is popularly known in Northeast Brazil as "alecrim-pimenta". The goal of the present work is to perform a quantitative analysis of timol, used as a marker in phytomedicine prepared from the leaves of L. sidoides, collected before, during and after the flower. At least three samples of tincture of L. sidoides were analyzed by HPLC. Among the samples analyzed, the tincture produced from the leaves after the flower showed slightly high concentration of timol (2,34 ± 0,06 mg/ml) when compared with before (1,97 ± 0,07 mg/ml) or during the flower (2,00 ± 0,03 mg/ml). The best period to collect leaves of L. sidoides seems to be after the flower.