Eight of them are Uruguayan, 10 foreign and the rest are joint ventures, said the newly created Institute for the Regulation and Control of Cannabis.
Their product will be sold in pharmacies under the groundbreaking law approved in December.
The law's mastermind, former leftist guerrilla President Jose Mujica, says it is a way to circumvent traffickers and stop wasting resources in fighting them.
Heavily criticized by the United Nations' International Narcotics Control Board, Uruguay's marijuana experiment is being closely followed by countries eager to find an alternative to the expensive and violent "war on drugs" spearheaded by the United States.
The Uruguayan government now has 15 days to choose up to five of the bidding companies.