Polycythaemia veraPegasys is indicated as monotherapy in adults for the treatment of polycythaemia vera. Essential thrombocythaemiaPegasys is indicated as monotherapy in adults for the treatment of essential thrombocythaemia..Chronic hepatitis BAdult patientsPegasys is indicated for the treatment of hepatitis B envelope antigen (HBeAg)-positive or HBeAg-negative chronic hepatitis B (CHB) in adult patients with compensated liver disease and evidence of viral replication, increased alanine aminotransferase (ALT) and histologically verified liver inflammation and/or fibrosis (see sections 4.4 and 5.1).Paediatric patients 3 years of age and olderPegasys is indicated for the treatment of HBeAg-positive CHB in non-cirrhotic children and adolescents 3 years of age and older with evidence of viral replication and persistently elevated serum ALT levels. With respect to the decision to initiate treatment in paediatric patients see sections 4.2, 4.4 and 5.1.Chronic hepatitis CAdult patientsPegasys is indicated in combination with other medicinal products, for the treatment of chronic hepatitis C (CHC) in patients with compensated liver disease (see sections 4.2, 4.4 and 5.1). For hepatitis C virus (HCV) genotype specific activity, see sections 4.2 and 5.1.Paediatric patients 5 years of age and olderPegasys in combination with ribavirin is indicated for the treatment of CHC in treatment-naïve children and adolescents 5 years of age and older who are positive for serum HCV-RNA.When deciding to initiate treatment in childhood, it is important to consider growth inhibition induced by combination therapy. The reversibility of growth inhibition is uncertain. The decision to treat should be made on a case by case basis (see section 4.4).