The synthesis and the structure-affinity relationship (S.A.F.I.R.) study for the 5-HT1A receptor sites of a novel series of 5(10→9)abeo-ergoline derivatives are presented. Most derivatives showed moderate to high affinity and selectivity for 5-HT1A receptor sites. The structure-affinity relationship pointed out the role of the substituent at position 8, and the outstanding importance of the reduction of the indole 2,3-double bond for achieving the highest 5-HT1A affinity and selectivity within the compounds presented.