The diversity and abundance of arthropods in feral and cultivated hop, Humulus lupulus L., in the major hop producing area of Canyon Co. in southern Idaho was measured during 2000 and 2001 from leaf and vacuum samples. A total of 133 arthropod species was collected from cultivated and feral hop during the 2-yr study. More species were collected using vacuum than leaf samples, but both methods indicated that feral sites were more diverse than cultivated sites. For leaf samples, the higher diversity of feral sites resulted from greater species evenness in feral than in cultivated sites. For vacuum samples, species evenness was similar, and species richness higher, in feral compared with cultivated sites. Cultivated hop had 5–10 times as many Tetranychus urticae Koch/leaf than feral hop; however, no statistically significant differences in the number of T. urticae/leaf on cultivated and feral hop were detected in either year. Hop plants in feral sites were infested with a greater number of Phorodon humuli (Schrank) in 2000 but not in 2001. The diversity and abundance of phytoseiid predators of T. urticae, did not differ between feral and cultivated hop.