In recent years, about twenty states have passed so-called medical marijuana laws. Typically, these laws permit individuals to lawfully purchase marijuana from licensed stores, provided they have a letter from their doctor recommending its use. In a number of these states, the price of medical marijuana is observed to be higher than that of the pot sold illegally just down the street. Use the reasoning in this chapter to explain (i) why people would be willing to pay a higher price for the medical marijuana, and (ii) why it might be misleading to compare the observed price of the medical variety with the observed price of the illegal weed.