Five new cavitands were prepared that have four pendant n-undecyl chains and “headgroups” connected by 2-carbon spacers. The headgroups were ∼OCH₂CONH-Ala-OCH₃, 1; ∼OCH₂CONH-Phe-OCH₃, 2; ∼OCH₂CONH-Ala-OH, 3; ∼OCH₂CONH-Phe-OH, 4; and ∼OCH₂CONHCH₂CH₂-thyminyl, 5. Pore formation by each cavitand was studied by use of the planar bilayer conductance experiment. All five compounds were found to form pores in asolectin bialyer membranes. Compounds 1–3 behaved in a generally similar fashion and exhibited open-close dynamics. Compounds 4 and 5 formed pores more rapidly, were more dynamic, and led more quickly to membrane rupture. Differences in the ion transport activity are rationalized in terms of structure and aggregate cavitand assemblies.