Round 4 – Monday, May 11, 2:00 pm
| Board | White | Rating | Result | Black | Rating |
| 1. | GM Gata Kamsky (2½) | 2798 | – | GM Joshua Friedel (2½) | 2568 |
| 2. | GM Yury Shulman (2½) | 2697 | – | GM Hikaru Nakamura (2½) | 2757 |
| 3. | GM Alexander Onischuk (2) | 2736 | – | IM Robert Hess (2) | 2545 |
| 4. | GM Varuzhan Akobian (2) | 2664 | – | GM Julio Becerra (2) | 2672 |
| 5. | GM Gregory Kaidanov (1½) | 2662 | – | GM Jaan Ehlvest (2) | 2649 |
| 6. | IM Michael Brooks (1½) | 2419 | – | GM Joel Benjamin (1½) | 2650 |
| 7. | GM Melikset Khachiyan (1½) | 2632 | – | IM Irina Krush (1½) | 2496 |
| 8. | IM Enrico Sevillano (1½) | 2549 | – | IM Samuel Shankland (1½) | 2464 |
| 9. | GM Larry Christiansen (1) | 2681 | – | GM Alexander Shabalov (1) | 2620 |
| 10. | IM Ray Robson (1) | 2542 | – | GM Ildar Ibragimov (1) | 2628 |
| 11. | Tyler Hughes (1) | 2293 | – | Charles Lawton (0) | 2350 |
| 12. | GM Boris Gulko (0) | 2631 | – | Doug Eckert (0) | 2278 |
Source: http://www.saintlouischessclub.org/US-Championship-2009-Round-4
Chess Daily News from Susan Polgar
Kamsky is winning I think.