Assuming that your grid is flat (no child bands or grouping, then you can try something like this:

            RowScrollRegion rowScrollRegion = this.ultraGrid1.ActiveRowScrollRegion;
            UltraGridRow lastVisibleRowInRowScrollRegion = null;
            for (int i = rowScrollRegion.VisibleRows.Count - 1; i >= 0; i--)
            {
                UltraGridRow row = rowScrollRegion.VisibleRows[i].Row;
                UIElement rowElement = row.GetUIElement(rowScrollRegion);
                if (rowElement != null &&
                    rowElement.Parent.Rect.Bottom > rowElement.Rect.Bottom)
                {
                    lastVisibleRowInRowScrollRegion = row;
                    break;
                }
            }

            UltraGridRow lastRowInGrid = null;
            for (int i = this.ultraGrid1.Rows.Count - 1; i >= 0; i--)
            {
                UltraGridRow row = this.ultraGrid1.Rows[i];                
                if (false == row.HiddenResolved)
                {
                    lastRowInGrid = row;
                    break;
                }
            }

            MessageBox.Show(this, "Scrolled to Bottom: " + (lastRowInGrid == lastVisibleRowInRowScrollRegion).ToString());

In my case ScrollBounds is set to ScrollToFill.  So I'll stop to search for a solution. Thank you, Mike.

Alan, I've tested you method and it's also not very accurate - when grid is scrolled to the bottom I always get ScrollPosition + VisibleRows.Count = DataSet.Rows.Count and it's the equal even if scroll is "one click before" it's maximum value. So, it doesn't work for me.

So, I got another question is there anyway to get vertical scrollbar Maximum value?

Amiram, definitely not. Because rect height is a value in pixels and ScrollPosition value is between 0 and data items count.