  We investigate the computational complexity of admissibility of inference
rules in infinite-valued {\L}ukasiewicz propositional logic (\L). It was shown
in [13] that admissibility in {\L} is checkable in PSPACE. We establish that
this result is optimal, i.e., admissible rules of {\L} are PSPACE-complete. In
contrast, derivable rules of {\L} are known to be coNP-complete.
