1. 1. Barre–Sinoussi, F. et al Science 220, 868–871 (1983). 2. Popovic, M. et al Science 224, 497–499 (1984). 3. Gottlieb, M. S. et al N. Engl J. Med. 305, 1425–1429 (1981). 4. Daniel, M. D. et al Science 228, 1201–1204 (1985). 5. Letvin, N. L. et al Science 230, 71–73 (1985). 6. Kanki, P. J., Alroy, J. & Essex, M. Science 230, 951–954 (1985). 7. Murphey–Corb, M. et al Nature 321, 435–437 (1986). 8. Fultz, P. N., et al Proc. natn. Acad. Sci. U.S.A. 83, 5286–5290 (1986). 9. Kanki, P. J., et al. Science 232, 238–242 (1986). 10. Franchini, G. et al. in AIDS Research and Human Retroviruses 3, 11–17 (1987). 11. Kornfeld, H., Riedel, N., Viglianti, A., Hirsch, V. & Mullins, J. I. Nature 326,610–613 (1987). 12. Clavel, F. et al Science 233, 343–346 (1986). 13. Albert, J. et al. in AIDS Research and Human Retroviruses 3, 2–10 (1987). 14. Clavel, F. et al. Nature 324, 691–695 (1986). 15. Guyder, M. et al. Nature 326, 662–669 (1987). 16. Ratner, L. et al. Nature 313, 277–284 (1985). 17. Sanchez–Pescador, R. et al Science 227, 484–492 (1985). 18. Muesing, M. A. et al Nature 313, 450–458 (1985). 19. Wain–Hobson, S., Sonigo, P., Danos, O., Cole, S. & Alizon, M. Cell 40, 9–17 (1985). 20. Ziff, E. B. & Evans, R. M. Cell 15, 1463–1475 (1978). 21. Proudfoot, N. J. & Brownlee, G. G. Nature 263, 211–214 (1976). 22. Guo, H.–G. et al in AIDS Research and Human Retroviruses (in the press). 23. Derse, D. et al J. Virol 61, 743–747 (1987). 24. Stephens, R. M., Casey, J. W. & Rice, N. R. Science 231, 589–594 (1986). 25. Seiki, M., Hattori, S., Hirayama, Y. & Yoshida, M. Proc. natn. Acad. Sci. U.S.A. 80,3618–3622 (1983). 26. Ratner, L. et al in AIDS Research and Human Retroviruses (in the press). 27. diMarzo Veronese, F. et al Science 231, 1289–1292 (1986). 28. Kan, N. C. et al Science 231, 1553–1555 (1986). 29. Arya, S. K., Guo, C., Joseph, S. F. & Wong–Staal, F. Science 229, 69–73 (1985). 30. Hirsh, V., Reidel, N. & Mullins, J. Cell 49, 307–319 (1987). 31. Fisher, A. G. et al. Science 233, 655–659 (1986). 32. diMarzo Veronese, F. et al. Science 229, 1402–1405 (1985). 33. Cease, K. B. et al. Proc. natn. Acad. Sci. U.S.A. 84, 4249 (1987). 34. Sodroski, J. et al. Nature 321, 412–417 (1986). 35. Feinberg, M. B., Jarrett, R. F., Aldovini, A., Gallo, R. C. & Wong–Staal, F. Cell46,807 (1986). 36. Knight, D. M., Flemterfelt, F. A. & Grayes, J. Science 236, 837–840 (1987). 37. Sanger, F., Nicklen, S. & Coulson, A. R. Proc. natn. Acad. Sci. U.S.A. 74, 5463–5467 (1977).