CDC, the Food and Drug Administration (FDA), state and local health departments, and public health and clinical stakeholders continue to investigate a nationwide outbreak of e-cigarette, or vaping, product use-associated lung injury (EVALI) (1). EVALI patients in Illinois, Utah, and Wisconsin acquired tetrahydrocannabinol (THC)-containing products primarily from informal sources (2,3). This report updates demographic characteristics and self-reported sources of THC- and nicotine-containing e-cigarette, or vaping, products derived from EVALI patient data reported to CDC by state health departments. As of January 7, 2020, among 1,979 (76%) patients with available data on substance use, a total of 1,620 (82%) reported using any THC-containing products, including 665 (34%) who reported exclusive THC-containing product use. Use of any nicotine-containing products was reported by 1,128 (57%) patients, including 264 (13%) who reported exclusive nicotine-containing product use. Among 809 (50%) patients reporting data on the source of THC-containing products, 131 (16%) reported acquiring their products from only commercial sources (i.e., recreational dispensaries, medical dispensaries, or both; vape or smoke shops; stores; and pop-up shops), 627 (78%) from only informal sources (i.e., friends, family, in-person or online dealers, or other sources), and 51 (6%) from both types of sources. Among 613 (54%) EVALI patients reporting nicotine-containing product use with available data on product source, 421 (69%) reported acquiring their products from only commercial sources, 103 (17%) from only informal sources, and 89 (15%) from both types of sources. Adolescents aged 13-17 years were more likely to acquire both THC- and nicotine-containing products from informal sources than were persons in older age groups. The high prevalence of acquisition of THC-containing products from informal sources by EVALI patients reinforces CDC's recommendation to not use e-cigarette, or vaping, products that contain THC, especially those acquired from informal sources. Although acquisition of nicotine-containing products through informal sources was not common overall, it was common among persons aged <18 years. While the investigation continues, CDC recommends that the best way for persons to ensure that they are not at risk is to consider refraining from the use of all e-cigarette, or vaping, products.