A new polymorph of pergolide mesylate or 8beta-[(methylsulfanyl)methyl]-6-propylergoline methanesulfonate, C(19)H(27)N(2)S(+).CH(3)SO(3)(-), is reported. Pergolide mesylate form II crystallizes in the trigonal system, which is unique for ergot derivatives. Although the hydrogen-bond system in form II differs completely from that in form I, the conformation of the pergolide moiety in various related structures is very similar.