In their thorough monograph of the genus Heloderma Wiegmann, Bogert and Martin del Campo (1956) noted the paucity of records for the Gila monster, Heloderma suspectum Cope, along the western extremity of its geographic range. The present paper reports the collection of two specimens and various encounters with six others in Yuma County, Arizona, together with brief notes on life history and habitat, an altitudinal low collection record for the subspecies I. s. cinctum Bogert and Martin del Campo, a far western record from Sonora of the subspecies H. s. suspectum Cope, an intergrade specimen from western Maricopa County, Arizona, and a possible record for California. For permission to examine and report the Gila monsters under his care, [...]