Well, if you feel it's an event, than the easiest thing to do is stat commenting out the code in one event at a time and see if the performance improves. 

For horizontal scrolling, I doubt the problem is in InitializeRow, but it couldn't hurt to test that theory. 

I have indeed changed the appearances on most cells.

I changed each columns celldisplay style to plaintext but it shows no improvement. I doubt it is performance related since my main grid (Right grid) has a horizontal scrollbar (which is only for him) and it scrolls smoothly. So my guess is that it is more event related.

 I am catching the cell activated event before/after rowregion scrolled.

 And also, I have a drawfilter that paints a few visual effects on some rows.

Hm, 200 columns could certainly be an issue. There may be some things you can do to speed it up.

You should probably take a look at the CellDisplayStyle property on the column. This property allows you to turn off certain functionality on the cells that you know your application is not using and thus gain some performance. 

What events of the grid are you handling?

Are you applying appearances to the grid cels or rows?

My situations is as followed:

• 2 ultragrids (Left and Right)
• Left has 4 columns
• Right has around 200 columns
• The right grid has a vertical scrollbar which the Left grid listens to. So when I drag the Right's scrollbar the Left grid follows it's position.
  The problem I have, is that when I let go of the Right's scrollbar he changes his position and a fraction later the left follows. (So maybe it has to do with the size of the grid, perhaps it has a hard time redrawing it ?). But I cannot change the fact that the grid has 200 columns since they represent a day in a timespan (which usually is a timespan of several months)

My computer has a duo core and 2 gig memory so I don't think it's a machine speed issue. I will check what version I am using, but we are using .NET Vol 2008 CLR 2.0

 ( As for the values in the grid, they are set manually)

I tested this out and it works fine for me using either the Before or AfterRowScrollRegions events. There is no noticable delay at all. 

What version of the grid are you using? I tested this with v7.2.

My guess is that you are probably using some features of the grid that are slowing down the scrolling of the left grid. Are you applying appearances to the grid? Are you using transparency? How big is the grid control? 

Are you using ValueLists or Editors? 

This might also be a question of machine speed. Are you developing on a particular slow machine?