At the present time there are continuing debates on the legal status of cannabis in New Zealand. Many of these debates have not given sufficient consideration to evidence concerning cannabis-related harm, much of which has been gathered here in New Zealand by the Christchurch Health and Development Study (CHDS) and the Dunedin Multidisciplinary Health and Development Study (DMHDS). We present a summary of this evidence, and recommendations for a cautious path forward for changing cannabis laws in New Zealand that aims at reducing cannabis-related harm.