In recent years there has been a dramatic progress in understanding how stimuli from different sensory modalities are integrated among each other. Multisensory integration results in a unitary representation of the world that strongly characterizes perception and cognition in humans. Knowledge about multi sensory integration has research techniques and approaches, including neurophysiology, experimental psychology, neuropsychology, neuroimaging, and computational modelling. This special issue aims at presenting an up-to-date integrative overview of the physiological, psychological, developmental, and functional processes associated with multisensory integration. The proposed collection of papers is organized thematically into sections, each featuring a state-of-the-art review of key themes in multisensory research, from more approaches in the animal, to the study of multisensory perception and cognition in humans. Specifically, this special issue will consider: The physiological mechanisms of multisensory processing in cortical and subcortical brain structures of model animal species, (rat, cat, and monkey); current biologically inspired computational modelling of multisensory integration; evidence about the multisensory contributions to perception in humans, as highlighted by psychophysical and neuropsychological evidence; the neural basis of multisensory processing in the human brain uncovered by recent neuroimaging techniques, including EEG, PET, fMRI; the consequences of the breakdown of normal sensory integration as shown by studies with techniques of brain stimulation in humans; developmental processes of multisensory perception in humans and the constrains for the emergence of multisensory processes in relation to sensory experience; the issue of crossmodal neuroplasticity concerning behavioral and neural changes following sensory deprivation. The challenge of this Research Topic is to provide an interdisciplinary context allowing to understand the basic principles of multisensory integration in humans and the key issues that this fascinating field of study rises for future research.