The structure and stability of 27 C-48 fullerene isomers have been computed at B3LYP. The most stable isomer (1) with the least number of shared pentagonal C-C bonds has a [5,6] type structure in C-2 symmetry, but isomers 2-4 are very close in energy (within 5 kcal/mol). The vertical ionization potential and the nucleus-independent chemical shift (NICS) at the cage center are computed for the first four most stable isomers to aid experimental study.