The biology of olive fruit fly, Bactrocera oleae (Rossi), was studied in the laboratory, greenhouse, and in canning olives, Olea europaea L., in relation to California regional climates. Adults survived in laboratory tests at constant temperatures and relative humidities of 5°C and 83%; 15°C and 59%; 25°C and 30%; and 35°C and 29% for 15, 6, 3, and 2 d without provisions of food and water and for 37, 63, 25, and 4 d with provisions, respectively. In a divided greenhouse, adults survived for 8–11 d in the warm side (36°C and 31% RH daytime) ; and in the cool side (26°C and 63% RH daytime) 10 d without provisions and 203 d with provisions. A significantly greater number of adults survived in the cool side than the warm side, and with provisions than without. First and last eggs were oviposited in olive fruit when females were 6 and 90 d old, respectively. The highest number of eggs was 55 per day in 10 olive fruit oviposited by 10 28 d-old females, with maximum egg production by 13–37 d-old females. A significantly greater number of ovipositional sites occurred in all sizes of immature green fruit when exposed to adults in cages for 5 d than 2 d. Adults emerged from fruit with a height of a 1.0 cm or a volume of ≥0.2 cm³. More than seven adults per 15 fruit emerged from field infested fruit with a height of 1.1 cm and volume of 0.1 cm³. Larval length was significantly different among the first, second, and third instars and ranged from 0.7 to 1.6, 2.4–4.3, and 4.8–5.6 mm at 14°C; 0.8–1.1, 1.9–2.9, and 3.9–4.4 mm at 21°C, and 0.7–1.3, 2.4–2.9, and 4.4–4.8 mm at 26°C, respectively. Survival of pupae to the adult stage was significantly lower at 26°C than 14°C or 21°C. The period of adult emergence began at 38, 14, and 11 d over a period of 8, 5, and 1 d at 14, 21, and 26°C, respectively. Findings were related to the occurrence and control of California olive fruit fly infestations.