Aims: In February 2012, new sentencing guidelines for drug offences became effective in all courts in England and Wales. An explicit aim was to reduce the length of sentences for drug “mules” and so make them more proportionate. Methods: This article examines their early impact drawing on data from the Court Proceedings Database and the Crown Court Sentencing Survey for importing/exporting a Class A drug. Findings: Overall, the guidelines have achieved their intended aim. The length of the average custodial sentence for drug trafficking fell following the introduction of the guidelines, largely due to taking defendants’ roles into account. Notably, three-quarters of those in “lesser” roles received sentences less than four years, representing an important change. Nonetheless, around 10% of mules received very long sentences due to the continued use of drug weight in sentencing. Conclusion: The new guidelines represent an internationally important innovation in drug policy reform.