The invention provides immunostimulatory compositions and use of those compounds in the preparation of medicaments for the treatment of disease as well as in vitro uses. In particular, the compositions of the invention include immunostimulatory oligoribonucleotides that incorporate a sequence-dependent immunostimulatory sequence motif. Specific modifications involving phosphate linkages, nucleotide analogs, adducts, and combinations thereof are provided. Compositions of the invention, which optionally can include an antigen, can be used alone or together with other treatments to stimulate or enhance an immune response. Also provided are compositions and methods useful for treating a subject having an infection, a cancer, an allergic condition, asthma, airway remodeling, or immunodeficiency. Immunostimulatory oligoribonucleotides of the invention are believed to stimulate Toll-like receptor 8 (TLR8).