C₃₃H₃₆0₆.0.5C₄H₉Br is trigonal, P3₁21, with α = 13.620 (8), c = 30.075 (26) Å; Z = 6; D_m = 1.192 Mg m^-3, μ = 0.719 mm^-1. Final R = 0.081 for 2286 reflections at 125 K. The structure was determined by direct methods in space group P3₁. The geometry of the host structure is consistent with space group P3₁21 whereas the Hamilton test favours space group P3₁. The structure of the guest molecule and its axially disordered orientation within the cavity are discussed.