The purpose of this project is to evaluate the design and implementation of the National Study of Caregiving (NSOC). NSOC was conducted in 2011 as an ancillary study to the National Health and Aging Trends Study (NHATS). NSOC focuses on the experience of caregivers who assisted NHATS participants with limitations in daily activities. The 30-minute telephone interview included questions about activities for which help was provided, duration and intensity of help, effects on helpers of providing assistance, support services used by helpers, and basic demographic information. The design called for interviewing all eligible caregivers as opposed to a single primary caregiver. Key questions to be answered include: Did participants who provided contact information to allow NSOC interviews differ from those who did not in terms of characteristics? Did the numbers and types of caregivers differ between participants who provided contact information and those who did not? How did participating caregivers differ from those who did not participate, in terms of demographics, caregiving role, relationship to NHATS sample person, and other characteristics? Were proxy respondents less likely to participate in NSOC? How successful was the effort to interview the complete caregiving network?