This is a study of lifetime alcohol and drug use among HCV+ patients who have received antiviral therapy. It will provide data needed to inform the development of evidence-based guidelines for treating HCV+ patients with a past or present history of alcohol and/or drug use. Studies of alcohol and drug use in patients with HCV are lacking because recent or current substance abuse is a contraindication for antiviral therapy, and systematic studies have not been conducted in light, moderate drinkers. The clinical and public health importance of establishing effective guidelines for treating HCV in drinkers and drug users is documented by reports that histories of drug use and heavy drinking are prevalent among HCV+ patients, that even moderate drinking may increase the progression of liver disease in HCV patients, that alcohol and drug use may reduce adherence to antiviral treatment regimens, that antiviral treatment may trigger relapses in former drug users, and that drinking impairs responsivity to interferon-based antiviral therapy. Research will be conducted in a sample of 500 HCV+ patients treated with pegylated interferon and ribavirin in the Sacramento Kaiser Permanente Medical Center during or after 2002. Clinical information relevant to patients' HCV treatment will be extracted from Kaiser's computerized databases on laboratory tests, pathology reports, and medical care utilization, and from paper medical reports that document HCV treatment monitoring. Detailed assessments of lifetime substance use will be employed to define drug use and the following alcohol drinking patterns, total consumption, total drinking frequency, intakes per day and per drinking day, and irregular drinking for four critical periods: 1) from the onset of regular drinking to the time patients learned they were HCV+, 2) from the time patients learned they were HCV+ to initiation of HCV treatment, 3) during HCV treatment, and 4) during the six months following completion of HCV treatment. Path analytic techniques will be employed to investigate: 1) direct effects of drinking patterns on sustained viral response (SVR, defined as no HCV RNA in serum six months after treatment ends); 2) indirect effects of drinking patterns on SVR mediated through reduced adherence to antiviral therapy; and 3) relations between drug use and SVR and moderating effects of drug use on the relation between drinking patterns and adherence. Probit and logistic regression analysis will be used to investigate clinically relevant parameters of significant relations between drinking patterns and SVR (e.g., how much do light, moderate, and heavy drinkers need to reduce their alcohol consumption to optimize SVR rates and for how long; do patients with an end-of-treatment viral response fail to obtain an SVR if they start drinking again after HCV treatment ends, and does antiviral treatment precipitate relapses in former substance abusers?). [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]