Room-temperature thermal rate constants for quenching and energy transfer have been determined for the individual fine-structure levels of the z(5)D(J)(o) term of the Fe atom in collisions with lie, Ar, and several molecular gases (N-2, O-2, H-2, and CH4). The z(5)D(J)(o) term is the upper level of a transition at 372 nm which is convenient for laser fluorescence detection of the Fe atom. Emission profiles from all excited levels were observed to be exponential, and total removal rate constants were derived. The rate constants for the molecular gases were significantly larger [in the range of (3-8) x 10(-10) molecule(-1) cm(3) s(-1)] than for the inert gases [(0.3-1.3) x 10(-10) molecule(-1) cm(3) s(-1)]. No evidence for collisional transfer to the neighboring b(3)H and a(3)D states was found, and upper limits for the collisional transfer rate constants are reported. Rate constants for intramultiplet transfer within the z(5)D(J)(o) state were determined for He and O-2. The intramultiplet rate constants for He summed over all final fine-structure levels roughly equaled the total removal rate constants, while they were similar to 10% of the total removal constants for O-2.