3,4-Dimethoxyamphetamine (3,4-DMA), or simply dimethoxyamphetamine (DMA), is a psychedelic drug of the phenethylamine and amphetamine families. It is one of the dimethoxyamphetamine (DMA) series of positional isomers.

The drug has been assessed in various biochemical and preclinical studies. It has been tried in humans at doses of up to 700 mg intravenously, with mescaline-like effects reported. 3,4-DMA is also orally active and has produced sympathomimetic effects at a dose of 160 mg. Its duration of action is unknown.

Its affinity (K_i) for the rat serotonin 5-HT_2A receptor has been assessed and was found to be 43,300 nM. For comparison, the affinity of para-methoxyamphetamine (PMA) was 33,600 nM, of 2,5-dimethoxyamphetamine (2,5-DMA) was 5,200 nM, and of 2,5-dimethoxy-4-methylamphetamine (DOM) was 100 nM in the same study. 3,4-DMA also showed affinity for the 5-HT₁ receptor (K_i = 64,600 nM). The drug has additionally been found to be a monoamine oxidase inhibitor (MAOI), with an IC₅₀Tooltip half-maximal inhibitory concentration of 20,000 nM for monoamine oxidase A (MAO-A), whereas it was inactive at monoamine oxidase B (MAO-B) (IC₅₀ > 100,000 nM).

3,4-DMA fails to produce stimulus generalization to dextroamphetamine in rodent drug discrimination tests, suggesting that it lacks psychostimulant- or amphetamine-like effects.

3,4-DMA produces 3-methoxy-4-hydroxyamphetamine (MHA) as its major metabolite in dogs and monkeys.