Individuals may face criminal prosecution for cartel activity in the UK, the maximum penalty is 5 years imprisonment and/or an unlimited fine. This Practice Note provides an outline of the kind of activities that will be caught by the criminal cartel offence prior to 1 April 2014, looking in particular at the requirement of dishonesty. Also, covered is the interplay with civil investigations against companies and seeking immunity from criminal prosecutions. Note—the criminal cartel offence changed on 1 April 2014, including the removal of the requirement for dishonesty. Following the entry into force of the Enterprise and Regulatory Reform Act 2014 on 1 April 2014, this practice note has been archived and is not maintained.