The low-energy electronic spectrum of the lead dimer is described by means of a multireference configuration interaction treatment based on a semicore relativistic effective core potential (RECP) including spin-orbit coupling. The X0(g)(+) ground state is found to be a heavy mixture of the ...sigma(2) pi(2) (3) Sigma(g)(-), the ...sigma pi(2) pi*(5) Pi(g), and ...pi(4) (1) Sigma(g)(+)Lambda-S states, underscoring the importance of the spin-orbit interaction in determining the electronic structure of this heavy system. The first excited state has 1(g) symmetry and is predominantly (3) Sigma(g)(-) but also with a heavy admixture of (5) Pi(g) character. The lowest-lying excited state as yet observed (A) seems to be the 2(u)(I) state, however, with a 0.09 Angstrom smaller computed r(e) value than for X0(g)(+). The B state with an experimental T-e value of 12 457 cm(-1) appears to be second 0(u)(-) state which arises from an avoided crossing between the ...sigma pi(3) (3) Pi(u) and the ...sigma(2) pi pi*(1) Sigma(u)(-)Lambda-S states. Another avoided crossing between the lowest two 0(u)(+) states is shown to produce the experimental C and F states, which possess the strongest transitions to X0(g)(+) of any of the low-lying Pb-2 states. The present computed radiative lifetime for the C state is in very good agreement with the measured value of Bondybey and English (1.5 mu s). The calculations also find that the F state’s lifetime is only about half as long as for the C state, whereas the experimental results give a smaller ratio of close to 0.1, indicating that nonradiative transitions may also be important for depopulating this state. Eleven other states are found to lie between the F and C states, despite their relatively small T-e value difference of 4500 cm(-1). Two of these are believed to have been observed in emission processes to the A state, but there is insufficient experimental data to make specific assignments in this case.