The ACTIVE study, a large-scale randomized controlled trial, evaluated the long-term effects of cognitive training on daily function in older adults. The study included 2832 participants living independently in six US cities. Participants were randomized to one of four groups: memory, reasoning, speed of processing, or a control group. The training interventions were 10 sessions each, with booster training at 11 and 35 months for the initial training groups. The main outcomes assessed self-reported and performance-based measures of daily function and cognitive abilities. Results showed that reasoning training significantly reduced difficulty in instrumental activities of daily living (IADL) compared to the control group. Speed of processing and memory training did not significantly affect IADL. Booster training for the speed of processing group improved performance-based functional measures of everyday speed of processing. Each intervention maintained effects on its specific targeted cognitive ability over 5 years. The study provides evidence that cognitive training can improve cognitive function and potentially reduce age-related decline in self-reported IADLs, which are precursors to dependence and increased health care use. However, the full extent of the intervention's impact on daily function may take longer to observe.The ACTIVE study, a large-scale randomized controlled trial, evaluated the long-term effects of cognitive training on daily function in older adults. The study included 2832 participants living independently in six US cities. Participants were randomized to one of four groups: memory, reasoning, speed of processing, or a control group. The training interventions were 10 sessions each, with booster training at 11 and 35 months for the initial training groups. The main outcomes assessed self-reported and performance-based measures of daily function and cognitive abilities. Results showed that reasoning training significantly reduced difficulty in instrumental activities of daily living (IADL) compared to the control group. Speed of processing and memory training did not significantly affect IADL. Booster training for the speed of processing group improved performance-based functional measures of everyday speed of processing. Each intervention maintained effects on its specific targeted cognitive ability over 5 years. The study provides evidence that cognitive training can improve cognitive function and potentially reduce age-related decline in self-reported IADLs, which are precursors to dependence and increased health care use. However, the full extent of the intervention's impact on daily function may take longer to observe.