A completely regular
Hausdorff space is an F′-space if disjoint cozero-sets have disjoint closures.
Here the theory of prime z-filters is applied to the study of F′-spaces. A
z-embedded subspace is one in which the zero-sets are all intersections of the
subspace with zero-sets in the larger space. It is shown that every z-embedded
subspace of an F′-space is also an F′-space. Also, a new characterization of
F′-spaces is obtained: Every z-embedded subspace is C∗-embedded in its
closure.