Thalamocortical synapses inform the cerebral neocortex about the external and internal worlds. The thalamus produces myriad thalamocortical pathways that vary in morphological, physiological, pharmacological and functional properties. All these features are of great importance for understanding how information is acquired, integrated, processed, stored and retrieved by the thalamocortical system. This paper reviews the properties of the afferents from thalamus to cortex, and identifies some of the gaps in our knowledge of thalamocortical pathways.