My first question would be: what have you been building in the vicinity? If you are talking about the frame rate at your colony: the more you build the slower your frame rate will be.
Things that slow down frame rate:
# of colonists
User-placed terrain voxels
Objects
Monorail in vicinity.
Massive numbers of building blocks
If you have the frame rate monitor turned on, you can see how it changes as you look at specific things (or in that general direction).
Try to limit colonists to around 12-16 (or less)
Use terrain sparingly
Don't build a rail unless you just really like rails (like me).
For massive builds, use HOLLOW designs to simulate massiveness. Think chocolate Easter bunny. It looks really big, but doesn't necessarily have to use a lot of chocolate. Building hollow walls takes skill and practice, but it will help with the frame rate on massive builds.
EDIT: Sorry, one last thing, which may not help with this, but might help with game loading on large maps. Turn off voxel cache, and/or delete voxel cache in the Options: Misc section before loading the game.
