Could you give a little more information please? Do you mean transparent (on/off appearance, like alpha testing or TBitmap.Transparent) or translucency (alpha blending)? Also, what API is this in (GDI, OpenGL, D3D)?

If it's standard Windows stuff then you can look at the obvious methods (DoubleBuffered = true and draw in the OnPaint method, manually double buffer your bitmaps where possible, use Graphics32, handle WM_EraseBkgnd, and so on).