42
You cannot catch a Rhydon in Black and White. You have to catch a Rhyhorn and level it up to level 42. Rhyhorn is only available in Pokemon White in White Forest.
Level 42.
Rhyhorn evolves into Rhydon at level 42 in Pokemon Emerald Version.
give a sooth bellto rhyhorn and train to level 42
Rhyhorn evolves into Rhydon at level 42.
Rhyhorn will evolve at Level 42.At level 42 in Rhydon.Rhyhorn evolves at level 42.
..........level rhyhorn to 42.....get a rhyhorn from safari and evolve it to rhydon
level 42
level 42
Level 42
a level 45 rhyhorn
level it up to level 42.