What is the longest possible series of consecutive captures? What is this the longest possible series of consecutive captures in a legal position? Here is an example of 25 on the same square, which is not required.

[FEN "q1kr2q1/1qnqnb2/2prp3/q2pK3/2P1P3/1QNQNB2/Q2R2Q1/3R3Q w - - 0 1"]

1. exd5 cxd5 2. cxd5 exd5 3. Bxd5 Qaxd5+ 4. Ncxd5 Rxd5+ 5. Nxd5 Nexd5 6. Qdxd5 Nxd5 7. Qbxd5 Qdxd5+ 8. Rxd5 Qxd5+ 9. Qaxd5 Bxd5 10. Rxd5 Qaxd5+ 11. Qxd5 Qxd5+ 12. Qxd5 Rxd5+ 13. Kxd5
Here's an example of 30 successive captures (White's 3rd to Black's 17th). It is the solution (from White's 3rd onwards) of a massacre proof-game found by Gerd Wilts &amp; Norbert Geissler.

[Title "Gerd Wilts &amp; Norbert Geissler.PDB CD-ROM 1998-Version"]
[StartPly "4"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1.d3 d6 2. Bg5 Bg4 3. Bxe7 Bxe2 4. Bxd6 Bxf1 5. Bxc7 Qxd3 6. Bxb8 Qxc2 7. Bxa7 Rxa7 8. Qxc2 Rxa2 9. Qxh7 Rxb2 10. Qxg8 Rxb1 11. Rxb1 Rxh2 12. Rxb7 Rxh1 13. Rxf7 Rxg1 14. Rxg7 Rxg2 15. Qxf8+ Kxf8 16. Kxf1 Rxf2+ 17. Kxf2 Kxg7