Aim: Layer 4 (L4) and 6 (L6) are the main thalamorecipient layers of the cerebral cortex. In addition, L6 provides direct projections back to the thalamus. The purpose of the study was to characterise the functional and anatomical properties of monosynaptic L4-to-L6A connections in the rat somatosensory (barrel) cortex. Methods: Semicoronal slices of barrel cortex (350 m thick) were prepared from juvenile Wistar rats. Dual whole-cell recordings were made from postsynaptic L6A pyramidal cells and presynaptic L4 spiny neurons. Biocytin-labelled cell pairs were reconstructed using Neurolucida (MicroBrightField, Colchester, VT). Results: Monosynaptic L4-to-L6A connections (n=12) were of high reliability and relatively low efficacy with an average unitary EPSP (uEPSP) of 0.35±0.20 mV. The uEPSP amplitude was either depressing or weakly facilitating during repetitive presynaptic action potentials at 10 Hz. Furthermore, uEPSPs at these connections could be divided into two types: When the presynaptic neuron was a spiny stellate, the uEPSP rise time and latency was long (7.4±1.2 ms and 3.2±1.6 ms, respectively) but shorter for presynaptic star pyramids (3.0±2.4 ms and 2.7±1.3 ms, respectively). Conclusion: L6A pyramidal cells receive different synaptic inputs from L4 spiny neurons which are specific for the presynaptic cell type. L4 spiny stellate neurons innervate predominantly the apical tufts of L6A pyramidal cells, while L4 star pyramidal neurons preferentially innervate the apical oblique and basal dendrites. Despite the difference in the electrotonic distances of the synaptic contacts to the soma at these two connection types, the efficacy and reliability are comparable.