This methodological report describes survey research and data collection methods employed for the first observational survey of cell phone use and texting by California drivers. This study was conducted by Ewald and Wasserman Research Consultants on behalf of the California Office of Traffic Safety and the Safe Transportation Research and Education Center at the University of California, Berkeley. The goal of the survey was to obtain a statewide, statistically representative observational sample. Vehicle drivers were observed at controlled intersections, such as traffic lights and stop signs, using a protocol similar to the National Occupancy Protection Use Study methodology published by the National Highway Traffic Safety Administration. Seventeen California counties were included in the sample frame, and 5,413 valid observations were made. Overall, 4.2% of drivers observed were using a cell phone while driving (phone to ear, manipulating a handheld device, talking on a handheld device, or talking via a headset or Bluetooth device). Because of the difficulty of observing hands-free use, previously used methods were applied to estimate this use at 4.8%. Therefore, an estimate of overall cell phone use in California during the survey period is 9%. California’s baseline level of cell phone use and driving will be a critical metric over the years as traffic safety stakeholders mobilize to conduct high-visibility enforcement campaigns, explore new policies, expand educational programs, and engineer countermeasures to increase safety on the roads.