The Czech Republic holds one of the highest numbers of men labelled as sexual delinquents worldwide who have undergone the irreversible process of surgical castration - a policy that has elicited strong international criticism. Nevertheless, Czech sexology has not changed its attitude towards 'therapeutic castration', which remains widely accepted and practised. In this paper, we analyse the negotiation of expertise supporting castration and demonstrate how the changes in institutional matrices and networks of experts (Eyal 2013) have impacted the categorisation of patients and the methods of treatment. Our research shows the great importance of historical development that tied Czech sexology with the state. Indeed, Czech sexology has been profoundly institutionalised since the early 1970s. In accordance with the state politics of that era, officially named Normalisation, sexology focused on sexual deviants and began creating a treatment programme that included therapeutic castration. This practice, the aim of which is to protect society from sex offenders, has changed little since. We argue that it is the expert-state alliance that enables Czech sexologists to preserve the status quo in the treatment of sexual delinquents despite international pressure. Our research underscores the continuity in medical practice despite the regime change in 1989. With regard to previous scholarship on state-socialist Czechoslovakia, we argue that it was the medical mainstream that developed and sustained disciplining and punitive features.