This study aimed to propose and validate a simple algorithm for grading the activity of chronic hepatitis C based on basic pathological features. A panel of 10 pathologists reviewed 363 liver biopsies and graded the activity of hepatitis according to their experience (reference activity). A consensus algorithm was established through a panel discussion, and stepwise discriminant analysis was performed to identify the key features used in the reference activity. The algorithm included piecemeal necrosis and lobular necrosis, while portal inflammation was excluded. The concordance between the reference activity and the algorithm-defined activity was substantial (84%, κ = .75). Discriminant analysis showed that piecemeal necrosis, lobular necrosis, and portal inflammation were independently used to grade the activity. The concordance between the reference activity and the statistical model-defined activity was also substantial (83%, κ = .73). The proposed algorithm is simple, reproducible, and applicable to a large number of biopsies, providing an easy means of scoring the activity in chronic hepatitis C.This study aimed to propose and validate a simple algorithm for grading the activity of chronic hepatitis C based on basic pathological features. A panel of 10 pathologists reviewed 363 liver biopsies and graded the activity of hepatitis according to their experience (reference activity). A consensus algorithm was established through a panel discussion, and stepwise discriminant analysis was performed to identify the key features used in the reference activity. The algorithm included piecemeal necrosis and lobular necrosis, while portal inflammation was excluded. The concordance between the reference activity and the algorithm-defined activity was substantial (84%, κ = .75). Discriminant analysis showed that piecemeal necrosis, lobular necrosis, and portal inflammation were independently used to grade the activity. The concordance between the reference activity and the statistical model-defined activity was also substantial (83%, κ = .73). The proposed algorithm is simple, reproducible, and applicable to a large number of biopsies, providing an easy means of scoring the activity in chronic hepatitis C.