DeEll, J. R. and Ehsani-Moghaddam, B. 2011. Timing of postharvest 1-methylcyclopropene treatment affects Bartlett pear quality after storage. Can. J. Plant Sci. 91: 853-858. This study investigated the effects of postharvest 1-methylcyclopropene (1-MCP) treatment timing on the ripening and physiological disorders of Bartlett pears during cold storage and subsequent shelf-life. Pears were held for 1, 3 or 7 d at 3°C after harvest and then treated with 0.3 µL L^-1 1-MCP for 24 h at 3°C. Fruit quality attributes were evaluated after 4 mo of cold storage at 0.5°C, plus 1 to 11 d at 22°C. All 1-MCP treatments reduced ethylene production, as well as delayed fruit softening and yellow color development. However, the most substantial benefit of 1-MCP observed was the marked reduction in disorders, especially senescent scald and internal breakdown. The results suggest that 1-MCP treatment 3 d after harvest provided the best balance of reduced disorder development during storage and the ability of Bartlett pears to soften adequately thereafter. Fruit treated with 1-MCP at 1 d after harvest did not soften as much as those treated 3 or 7 d after harvest, while treatment after 7 d provided less control of disorders than treatment after 1 or 3 d.