The diagnosis of subepidermal auto-immune bullous dermatosis is usually based on immunofluorescence which demonstrates IgA, IgG, IgM or C3 on dermo-epidermal junction. However in some instance, this technique could not be performed. Here we report an alternative to immunofluorescence. It is a preembedding technique of immunolabelling using horseradish peroxidase, on fresh tissue without any freezing, before an inclusion in wax. So the observation of the labelling is possible with a standard microscope. This technique has been applied to 7 patients with various sub-epidermal auto-immune bullous dermatosis whose diagnosis was confirmed elsewhere by immunoelectron microscopy. It was as specific and sensitive than immunofluorescence whatever the bullous dermatosis.