We construct M-theory curves associated with brane configurations of S
U(N), SO(N) and Sp(2N) 5D supersymmetric gauge theories compactified o
n a circle. From the curves we can account for all the existing differ
ent SU(N) held theories with N-f less than or equal to 2N. This is the
correct bound for N greater than or equal to 3. We remark on the exce
ptional case SU(2). The bounds obtained for SO(N) and Sp(2N) are N-f l
ess than or equal to N - 4 and N-f less than or equal to 2N + 4, respe
ctively. (C) 1997 Elsevier Science B.V.