We consider supersymmetry algebras in space-times with arbitrary signature
and minimal number of spinor generators. The interrelation between super Po
incare and super conformal algebras is elucidated. Minimal super conformal
algebras are seen to have as bosonic part a classical semisimple algebra na
turally associated to the spin group. This algebra, the Spin(s, t)-algebra,
depends both on the dimension and on the signature of space-time. We also
consider maximal super conformal algebras, which are classified by the orth
osymplectic algebras. (C) 2001 Elsevier Science B.V. All rights reserved.