Abstract.It is proved that if E is an arbitrary nuclear space and F is an arbitrary infinite-dimensional Banach space, then there exists a fundamental (basic) system V of balanced, convex neighborhoods of zero for E such that, for each Kin i*~, the normed space Ev is isomorphic to a subspace of F. The result for F=lv (1 ^/>^oo) was proved by A. Grothendieck. (i) A locally convex space is nuclear if and only if it is isomorphic to a subspace of a product space (s)1, where / is an indexing set and (s) is the Fréchet space of all rapidly decreasing sequences.(ii) Every infinite-dimensional Banach space contains a closed infinitedimensional subspace which has a Schauder basis.1Recall that for a balanced, convex neighborhood V of zero in a locally convex space E, Ev is a normed space which is norm-isomorphic to (M,p\M), where/? is the gauge of V and M is a maximal linear subspace of £ on which/; is a norm; Ev is the completion of Ev. Denote by (s) the nuclear Fréchet space of rapidly decreasing sequences, so that (s) = j(A):sup \nkXn\ < co, k = 1, 2, • • •),