Activity patterns and time budgets of Andean (or spectacled) bears Tremarctos ornatus were examined in a high-altitude (3000–4000 m) mixed grassland–cloud forest environment in the Apolobamba Range of northern Bolivia. Two males were captured, fitted with motion-sensitive radio-collars and monitored during 1998–1999. As with many cryptic species, Andean bears had been assumed to be nocturnal, but both bears in our study were diurnal. Activity generally began around 06:00 h (near sunrise) and lasted until 20:00–21:00 h (sunset), with reduced activity during 11:00–14:00 h. Bears rested for 1–2 h during daylight hours, generally in two or more brief periods, and slept 9–12 h at night. Few differences were observed between activity patterns or time budgets during the dry season (April–September) and rainy season (October–March). Averaged across all hours and both seasons, each bear was active 53% of the time. This level of activity was similar to that of other species of bears (generally 50–60%), suggesting either that Andean bears are well adapted to living in an environment where fibrous bromeliads constitute the bulk of their diet or that our two study bears could subsist there only because they were both small-sized individuals.