5-APB, commonly marketed as ‘benzofury’ is a new psychoactive substance and erstwhile ‘legal high’ which has been implicated in 10 recent drug-related deaths in the UK. This drug was available on the internet and in ‘head shops’ and was one of the most commonly sold legal highs up until its recent UK temporary ban (UK Home Office). Despite its prominence, very little is known about its pharmacology. This study was undertaken to examine the pharmacology of 5-APB in vitro. We hypothesised that 5-APB would activate the dopamine and 5-HT systems which may underlie its putative stimulant and hallucinogenic effects. Autoradiographic studies showed that 5-APB displaced both [125I] RTI-121 and [3H] ketanserin from rat brain tissue suggesting affinity at the dopamine transporter and 5-HT 2 receptor sites respectively. Voltammetric studies in rat accumbens brain slices revealed that 5-APB slowed dopamine reuptake, and at high concentrations caused reverse transport of dopamine. 5-APB also caused vasoconstriction of rat aorta, an effect antagonised by the 5-HT 2A receptor antagonist ketanserin, and caused contraction of rat stomach fundus, which was reversed by the 5-HT 2B receptor antagonist RS-127445. These data show that 5-APB interacts with the dopamine transporter and is an agonist at the 5-HT 2A and 5-HT 2B receptors in the rat. Thus 5-APB's pharmacology is consistent with it having both stimulant and hallucinogenic properties. In addition, 5-APB's activity at the 5-HT 2B receptor may cause cardiotoxicity.