Porygon can only be evolved through trading while holding the "upgrade" item. This will evolve it into porygon2. It can be evolved again by trading a porygon2 while it is holding the "dubious disc" item which will evolve it into porygon-Z
Porygon
Find a upgrade to evolve Porygon to Porygon2. The upgrade should be in different places depending on the game. -seal339
Porygon 2 and porygon- z
it evovle at 16
there is porygon-2 but not porygon. porygon-2 is in oil field hideout
give it to porygon and trade to get porygon-2
Yes, you can breed Porygon with Ditto to obtain a Porygon Egg.
Have a porygon hold upgrade then trade and boom its a porygon 2.
You have to have the up-grade then trade it to evolve into Porygon-2 and then a dubilicius disc for Porygon-2 to evolve into Porygon-Z
You can give the Upgrade to Porygon and then trade it to a friend to make Porygon evolve into Porygon2, in order to evolve Porygon2 then give a Dubious Disc to Porygon2 and then trade it to someone and it'll evolve into a Porygon-Z.
Porygon can evolve into Porygon 2, while holding an Upgrade and traded. Even further, Porygon 2 can evolve into Porygon Z, while holding a Dubious Disc and traded.
you evolve a porygon by trading it. then you get porygon 2. then you evolve porygon 2 by trading. then you get porygon-z. P.S. if you still want your porygon 2/Z trade back. P.S.S.to make sure you get it back trade with your brother,sister,friend ECT.