Thanks BB. The pinned arrary sounds very interesting. I should have made one thing clearer. I actually have a picturebox/bitmap that is 512 x 512 pixels and I need to add blocks of 512 x 4 to it at intervals of around 100mS. Obviously I need to specify the location (within in the main picturebox) of the new block that is added each time, although it will always be four lines down from the last block. I'm not sure if that changes your recommendations for a fast pixel plotter.

I really appreciate your help with this.