For any time bound f , let H(f ) denote the hierarchy conjecture which means that the restriction of the numbers of work tapes of deterministic Turing machines to b ∈ N generates an infinite hierarchy of proper subclasses DTIME b (f ) ⊂ DTIME(f ). We show that H(f ) implies separations of deterministic from nondeterministic time classes. H(f ) follows from the gap property, G(f ), which says that there is a time-constructible f2 such that f ∈ o(f2) and DTIME(f ) = DTIME(f2). G(f ) implies further separations. All these relationships relativize.