  We present experimental atomic lifetimes for 12 levels in Sb I, out of which
seven are reported for the first time. The levels belong to the 5p$^2$($^3$P)6s
$^{2}$P, $^{4}$P and 5p$^2$($^3$P)5d $^{4}$P, $^{4}$F and $^{2}$F terms. The
lifetimes were measured using time-resolved laser-induced fluorescence. In
addition, we report new calculations of transition probabilities in Sb I using
a Multiconfigurational Dirac-Hartree-Fock method. The physical model being
tested through comparisons between theoretical and experimental lifetimes for
5d and 6s levels. The lifetimes of the 5d $^4$F$_{3/2, 5/2, 7/2}$ levels (19.5,
7.8 and 54 ns, respectively) depend strongly on the $J$-value. This is
explained by different degrees of level mixing for the different levels in the
$^4$F term.
