+Rahim Zulfiqar Ali asks why VLOOKUP(,,,True) returns certain wrong answers when the table is not sorted. The better question would be how it returns the right answer at all when you break the rules. Today, I explain the gory details behind the Binary Search used by the VLOOKUP(,,,True) and show how manipulating key values at the quartiles of the lookup table can send the VLOOKUP into the wrong quadrant of the table. Bottom line: Don't use the VLOOKUP(,,,True) with an unsorted table. Or.... just use VLOOKUP(,,,False) like 99% of the rest of the world.