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Yes, of course (assuming you're talking 120 VAC and normal non-heavy demanding power equipment or heaters).
http://electrical.about.com/od/wiringcircuitry/a/extentioncordchoices.htm

Excerpted from the electrical info on the previous webpage...when using extension cords for heavy duty or high wattage heater:

"Extension cords should at least have a rating equal to or greater to the requirements needed to run a tool effectively. Extension cord lengths 50 feet or less can be used based upon the following chart, but runs over 50 feet should implement the next heavier sized cord to accommodate voltage drop in the cord due to the natural resistance of the wire."

{See webpage for electrical chart}

Are we talking a flat race or steeplechase?