Primordial nucleosynthesis is reexamined in the context of a detailed comparison of theory and observation. A new argument is presented to show how the observed abundances of D and 3He can be used to derive a lower bound to the nucleon density. The authors define a conservative range for the nucleon-to-photon ratio: η = (3 - 10)×10-10. New observations of 7Li are consistent with the abundances of D and 3He and help to define a reasonable range: η = (4 - 7)×10-10. In either of these ranges the predicted and observed abundances of D, 3He, and 7Li are all in concordance. The upper bounds correspond to ΩN ≤ 0.14 - 0.19, and it is concluded that nucleons fail to close the universe by at least a factor of 5 - 7. The authors review the recent observational data on 4He and conclude that there is complete consistency between the predicted abundance of 4He and those of the other light elements.