Temperature-dependent development ofCoccinella trifasciata LeConte from Corvallis, Oregon, was assessed for the general population and compared among a subset of isofemale lines. All eggs died at 10 and 34°C. Survival ranged between 63.3–96.7% from 18–34°C. Development from oviposition to adult ranged from 44.2 days at 18°C to 11.1 days at 34°C. Mean adult weight did not differ among temperatures, and was 15.2 mg overall. For the species, heat-unit requirements for development from egg to adult were 227 degree-days above a developmental threshold of 12.7°C. Values for the developmental threshold differed among isofemale lines, and ranged from 11.4–14.5°C with heat-unit requirements ranging from 186–260 degree-days above their respective threshold. The isofemale line producing the fastest rate of immature development at 18°C was characterized by a heat-unit requirement of 260 degree-days above a developmental threshold of 11.4°C. The isofemale line producing the slowest rate of immature development at 18°C was characterized by a heat-unit requirement of 186 degree-days above a developmental threshold of 14.5°C. Implications of using isofemale lines in culturing biological control agents are discussed.