You can see the current list of MMs here You might need a MM in item - cash trade item - game gift trade(not tradable gift) game gift - cash trade et cetera To put it simple, you might need a MM whenever cash or one or more untradable item(gift)is involved. You don't need a MM in item - item trade item - game gift trade game gift - game gift trade etc.. You don't need a MM when both traders can trade their items at the same time(all items&gifts are tradable and cash is not involved) MM trade howto : (examples are quoted) Step by step Each party should make sure that his opponent is not a marked scammer. Either party gets a MM from the MM list The Buyer(who pays cash), Seller(who has the item), MM joins multi-user chat. The MM introduces himself(herself) Both users confirm that he is an official middleman by searching his SteamID. If anything suspicious, they can ask whatever questions until they are satisfied. Both users should not just visit the SteamREP link the MM gives. He might be an impersonator! Both users SHOULD copy MM's Steam Profile address and search it on SteamREP. To see how to search one's steam profile on SteamREP, visit here. Both users tell the MM about the trade. Both users should agree on the trade info by saying so. Both users tell their paypal id The MM requests a trade to the Seller. The Seller give the item to MM. MM confirms that he/she got the item by saying so. The Buyer sends the money(fee should be payed by the Buyer if that was the deal) The Buyer informs that the transaction has been completed. The Seller confirms he/she got the exact amount of money. The MM requests a trade to the Buyer. The MM gives the item to the Buyer. Both users should copy the chat log and take screenshots of the chat just in case.