This study was conducted to evaluate the efficacy of thyme oil in suppressing Alternaria alternata (Fr.:Fr.) Keissl in vitro and in vivo as fumigant and contact treatments. Thyme oil possessed great fumigant and contact toxicity against A. alternata at different concentrations in vitro. Irreversible inhibition of fungal growth could be caused by exposure to 500 mu L/L thyme oil as a fumigant for 6 and 12 days. The spores of A. alternata were completely suppressed 6 h after incubation in potato dextrose broth (PDB) by 2000 mu L/L of thyme oil. The thyme oil as a fumigant at 66.7 mu L/L showed a significant inhibition effect on A. alternata of cherry tomatoes stored at 25 degrees C for 5 days. Thyme oil at 500 mu L/L showed a significant contact inhibition effect on A. alternata of cherry tomatoes stored at 25 degrees C for 3 days. (C) 2010 Elsevier Ltd. All rights reserved.