Where do the gym leaders go after you beat them in heart gold?

After you defeat a Gym Leader in HeartGold and SoulSilver, they remain in their Gym. You can re-battle them at any time for rematches, and their Pokemon will be stronger.

However, you can find some Gym Leaders outside of their Gyms after you've beaten the Elite Four:

* Whitney can be found on Route 36, where she's training Miltank.

* Falkner can be found on Route 34, where he's training Pidgey.

* Bugsy can be found on Route 35, where he's training Scyther.

* Chuck can be found on Route 38, where he's training Poliwhirl.

* Jasmine can be found on Route 40, where she's training Steelix.

* Pryce can be found on Route 42, where he's training Piloswine.

* Clair can be found on Route 44, where she's training Kingdra.

* Koga can be found on Route 45, where he's training Ariados.

* Bruno can be found on Route 47, where he's training Onix.

* Karen can be found on Route 48, where she's training Houndoom.

It's worth noting that while you can battle these Gym Leaders again after defeating the Elite Four, they won't have any new Pokemon or changes to their teams.