Technical Abstract: Sunflower stem weevils (Cylindrocopturus adspersus) and their larval parasitoids were collected from stems of four native sunflower species (Helianthus annuus, H. nuttallii, H. pauciflorus, and H. petiolaris) from 147 sites across eight states in 2003 and 2005. Native H. annuus constituted the majority of the sunflower populations. Sunflower stem weevil larvae were found at nearly all locations and in all species except H. nuttallii for which only one population was sampled. Mean weevil densities were significantly higher in sunflower stalks that were larger in diameter. Mean weevil densities were higher at sites located at middle longitudes and latitudes. After accounting for the effects of stalk diameter and location (both latitude and longitude), weevil densities did not differ among the four sunflower species nor did they differ as a function of elevation. Sunflower stem weevils in H. annuus and H. petiolaris were attacked by six species of parasitoids. No parasitoids were found in H. nuttallii or H. pauciflorus stalks. C. adspersus were twice as likely to be attacked by a parasitoid when feeding on H. petiolaris than H. annuus. Furthermore, the likelihood that C. adspersus would be parasitized decreased with increasing elevation. All parasitoid species have been previously reported attacking C. adspersus larvae in cultivated sunflower. Species richness was less diverse in these collections than from earlier studies of cultivated sunflower. Our findings suggest that the species of larval parasitoids attacking C. adspersus in native sunflowers have successfully made the transition to cultivated sunflower to parasitize this pest species.