||Bis(sym-collidine)iodine(I) tetrafluoroborate, a electrophilic iodonium ion transfer reagent has been used in combination with methyl sulfoxide to convert cyclic alkenes and enol ethers to the corresponding (alpha)-iodocarbonyl compounds. With conformationally biased alkenes the reactions proceeded stereospecifically giving axial iodoketones. Various unsaturated carbohydrates were converted into novel (alpha)-iodo-(alpha),(beta)-unsaturated lactones. Bis(sym-collidine)iodine(I) tetrafluoroborate was found to react with alkenes in the absence of any externally added nucleophiles to give moderate yields of vicinal iodofluorides. Reaction of the reagent with various unsaturated carbohydrates proceeded with high stereo- selectivity giving the diaxial "IF" adducts as the major products. The analogous reagent bis(sym-collidine)iodine(I) hexafluorophosphate was also found to be efficient for the iodofluorination of alkenes. Aspects of regio- and stereochemistry as well as mechanistic considerations involved in the reactions are discussed.