Options Trading Tutorial - If I exercised stock options and later sold the stock, what is my cost basis

If I exercised stock options and later sold the stock, what is my cost basis - the price I bought the stock at?

or the market value the day I bought the stock? Thanks!

1. your cost basis is the price you bought (strike price).
I am assuming you mean options you purchased on the open market. If you exercised call options to buy the stock your cost basis is the price you paid for the call options plus the price you paid for the stock. So, for example, if you bought 2 $50 strike call options for XYZ corporation and paid $109.95 (including commissions) for the options and then exercised them your cost basis would be ($50 x 200) + 109.95 + any commission for the stock purchase. So if you paid a $9.95 commission for the stock purchase your total cost basis would be $10,119.90. ----- If you mean options you obtained as compensation for services, see http://www.fairmark.com/capgain/basis/options.htm
Your basis is exercise price of the options (stock purchase price) PLUS the option premium (cost of options exercised) PLUS commissions and fees.