For any even positive integer 2n and any positive integer m we construct a class of regular self-adjoint and non-self-adjoint boundary value problems whose spectrum consists of at most (2n 1)m + 1 eigenvalues. Our main result reduces to previously known results for the cases n = 1 and n = 2: In the self-adjoint case with separated boundary conditions this upper bound can be improved to n(m + 1):