A $20 bill from 1934 will range in value from anywhere between $25 to $60, with $35 being the average sale price. The amount you get for the bill will depend on its condition and the buyer's attitude. 1934 was the year in which the bill's redemption was changed from gold to silver, also known as 'Lawful Money'. To read more about the $20 bill's history, visit: http://www.ask.com/wiki/United_States_twenty-dollar_bill.
The value of a 1934 twenty dollar bill depends on a number of things: you need to check the serial number, the color of the seal, the series and its condition. You can visit http://www.measuringworth.com/uscompare/ for more information on this topic
To determine the value of a 1934 twenty dollar bill, the following factors has to be considered. The color of the seal, the grade (condition), the serial number and the series. I encountered one time in ebay that it is being sold at $70. Just don't know if it has been sold.