The n-alkyl bromides with 6 to 10 carbons induce formation of vesicles of 5 to 100 micrometer diameter from the small vesicles (0.1 micrometer average diameter) produced by disruption of the discs from frog rod photoreceptors. The n-alkanes, n-alkyl iodides and n-alkyl chlorides are relatively ineffective. The formation of large vesicles is independent of calcium concentration and is distinguished from fusion processes previously reported by the large number of vesicles involved. The results reported here together with others suggest the occurrence of multiple fusion (and/or rupture-resealing) events between vesicles, induced by the n-alkyl bromides.