Immunostimulatory oligoribonucleotides (ORN) featuring 5′-triphosphates and various 5′-triphosphate analogs are provided. Also provided are physiologically acceptable salts of the immunostimulatory ORN and pharmaceutical compositions containing the immunostimulatory ORN of the invention. ORN of the invention are useful as adjuvants and can be combined with an antigen to promote an antigen-specific immune response. ORN of the invention are also particularly useful for promoting a Th1-type immune response. Also provided are methods of use of the compounds and pharmaceutical compositions of the invention to enhance an immune response in a subject, as well to treat a number of conditions including cancer, infection, allergy, and asthma, and to vaccinate a subject against an antigen.