2019-Aug-16: A handful of you reported issues accessing puzzles yesterday. This was caused by a "repair" to the server I made, heh. If you are still having issues, send me the troublesome URL in the address bar so I can investigate. Thank you for your patience! — Jim

Tough Killer Sudoku, Volume 4

Each booklet contains a collection of eight different puzzles, 1-per-page, with a page of answers in the back. The booklets are ordered by ascending difficulty -- the puzzles in book 100 are much harder than the puzzles in book 1. All these puzzles have a single unique solution.

These puzzles are in PDF format and need the Adobe Acrobat Reader to view or print.

You can also download all 800 of these puzzles, in the 4-per-page format ( with hints and answers, with answers but no hints, or with neither hints nor answers).

Want to save even more trees? Try the online version of these puzzles.

Here's a handy cheat-sheet of candidate cage sets that makes it easier to eliminate numbers.

Problems printing puzzles? Try these work-arounds.

Out of tough puzzles? Here's 800 more!.