Objective To study the causes and influential factors for relapse after drug withdrawal in patients with chronic hepatitis C( CHC). Methods One hundred and one cases of CHC,including 36 males and 65 females,who were outpatients or inpatients in our hospital,were enrolled as subjects. Twenty-six patients had compensated cirrhosis,and seventy-five had chronic hepatitis. Their age ranged from 19 to 71 years. All patients had no treatment history. Routine blood indices,biochemical parameters,autoantibodies,thyroid function,hepatitis C viral load( HCV RNA),and hepatitis C virus( HCV) genotypes were evaluated before treatment. Liver function,routine blood indices,and HCV RNA load were evaluated at weeks 4,12,24,and the end of treatment,as well as 12,24,48,72,and 96 weeks after treatment. The follow-up time after drug withdrawal was 96 weeks. All patients were divided into relapse group and sustained response group,according to whether HCV RNA was detected or not. Patients in the relapse group were further divided into two groups: relapse within 24 weeks and relapse after achieving sustained virological response( SVR). The effects of baseline levels,4-week virological response rates,biochemical response rates,and treatment regimen on relapse were assessed. Between-group comparison of categorical data was performed by χ2test,and between-group comparison of continuous data was performed by t test. Results In all patients,71 patients( 70. 3%) had rapid virological response( RVR),90 patients( 89. 1%) had early virological response,and 9 patients( 8. 9%) had no response or restored HCV RNA during treatment. Among 92 patients( 91. 1%) with end-of-treatment virological response( ETVR),28patients( 30. 4%) had genotype 1b,while 64 patients( 69. 6%) had non-1 genotypes. Among 92 patients with ETVR,60 patients( 65. 2%) received the standard treatment,while 32 patients( 34. 8%) received the non-standard treatment. During a 2-year follow-up of 92 patients with ETVR after drug withdrawal,30 patients( 32. 6%) had relapse after drug withdrawal,including 13 patients( 43. 3%)who had relapse within 24 weeks after drug withdrawal,and 17 patients( 56. 7% of patients with relapse; 21. 5% of patients with SVR;18. 5% of patients with ETVR) who had relapse after achieving SVR. There were significant differences in age,HCV RNA load,cirrhosis,4-week alanine aminotransferase( ALT) normalization rate,RVR rate,and non-standard treatment rate between the relapse group and the non-relapse group( t = 2. 624,P < 0. 05,χ2= 15. 199,P < 0. 05; χ2= 4. 469,P < 0. 05; χ2= 7. 352,P < 0. 05; χ2= 7. 453,P <0. 05; χ2= 19. 950,P < 0. 05). The genotype and gender were not influencing factors for relapse. There were significant differences in HCV RNA load,cirrhosis,and standard treatment rate between patients with short-term relapse and relapse after achieving SVR( P < 0. 05).Conclusion The causes for relapse after drug withdrawal in patients with CHC involve age,viral load,cirrhosis,ALT normalization rate,RVR rate,and non-standard treatment. The high viral load and non-standard treatment are the main causes for short-term relapse.