  We review the basic structure of the higher spin extension of D=4, N=8 AdS
supergravity. The theory is obtained by gauging the higher spin superalgebra
shs^E(8|4) by a procedure pioneered by Vasiliev. The algebra shs^E(8|4) is a
subalgebra of the enveloping algebra of OSp(8|4). The physical states of the
theory are in one to one correspondence with the symmetric product of two
OSp(8|4) singletons. This singleton theory, which may be viewed in a certain
limit as the supermembrane theory on AdS_4 x S^7, is expected to describe the
dynamics of the higher spin theory. Thus, the higher spin N=8 supergravity on
AdS_4 is conjectured to describe the field theory limit of M-theory on AdS_4 x
S^7.
