The effects of 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action, on the ripening and quality of Fantasia nectarines were examined. Fruit were harvested from two commercial orchards and subsequently exposed to 1 μL L-1 of 1-MCP for 24 h at 0°C. Following treatment, fruit were held at 0°C for 0, 2, or 4 wk, and then assessed for quality during a ripening period at 23°C. 1-MCP treatment improved postharvest firmness retention in nectarines after 0 and 2 wk at 0°C plus 4 days at 23°C. Soluble solids concentration (SSC) was lower in nectarines treated with 1 MCP and held for 0 or 4 wk at 0°C, compared with similar non-treated fruit. The peel ground color change from green to yellow was also delayed by 1-MCP. Nectarines treated with 1-MCP exhibited less CO2 and hydrophobic volatile production during 14 days at 23°C, compared with non-treated fruit. The overall inhibition of fruit ripening by 1-MCP appears transitory in Fantasia nectarines. Chilling injury was observed after 4 wk of storage at 0°C and 1-MCP-treated fruit had less visual chilling-related injury but greater chilling-induced flesh hardening. Further research is needed to determine the effects of 1-MCP on different chilling injury symptoms in nectarines. Key words: 1-MCP, fruit quality, ripening, storage, shelf-life, Prunus persica