We recently coined the phrase ‘psychobiotics’ to describe an emerging class of probiotics of relevance to psychiatry [Dinan et al., Biol Psychiatry 2013;74(10):720–726]. Such “mind-altering” probiotics may act via their ability to produce various biologically active compounds, such as peptides and mediators normally associated with mammalian neurotransmission. Several molecules with neuroactive functions such as gamma-aminobutyric acid (GABA), serotonin, catecholamines and acetylcholine have been reported to be microbially-derived, many of which have been isolated from bacteria within the human gut. Secreted neurotransmitters from bacteria in the intestinal lumen may induce epithelial cells to release molecules that in turn modulate neural signalling within the enteric nervous system and consequently signal brain function and behaviour of the host. Consequently, neurochemical containing/producing probiotic bacteria may be viewed as delivery vehicles for neuroactive compounds and as such, probiotic bacteria may possibly have the potential as a therapeutic strategy in the prevention and/or treatment of certain neurological and neurophysiological conditions.