Heterocyclic chem. continues to be in the focus of life science-oriented research. Fluorine, a unique tool for finetuning biol. properties, offers an extra bonus in this context. The lecture features three pertinent issues. First, proven and novel routes to F-, CF3- and OCF3-substituted heterocycles will be reviewed. Next, the specific merits of the organometallic approach to the functionalization of "naked" core structures will be portrayed. Finally, it will be demonstrated how any vacant position in pyridines, quinolines, pyrimidines, pyrazoles and indoles can be substituted and, in particular, functionalized selectively and reliably. [on SciFinder (R)]