  I review the basic processes that may be used to develop a chemical
evolutionary sequence for low-mass starless cores. I highlight observational
results from the Arizona Radio Observatory-Green Bank Survey. Observations were
performed with the SMT 10-m, ARO 12-m, and GBT 100-m toward a sample of 25
nearby (D < 400 pc) low-mass starless cores which have radiative transfer
models of the 850 $\mu$m emission and observed SED (160 - 1300 um). The cores
were observed in the lines of NH3 (1,1) and (2,2), o-NH2D 1_{11} - 1_{01}, C2S
1_2 - 2_1, C3S 4 - 3, HCN 1 - 0, HC5N 9 - 8, HC7N 21 - 20, C18O and C17O 2 - 1,
and p-H2CO 1_{01} - 0_{00}.
