The authors describe a prepolymerized methyl methacrylate embedding technique for undecalcified bone biopsies. They have a 588 biopsies experience. Results are obtained in three days. The use of a prepolymerized Medium reduces retraction artefacts. Structures are well preserved, so morphometric analysis is easy. All routine colorations can be done after deplastification. It is especially easy to recognize the osteoid tissue, the method consequently being useful in the diagnosis of osteomalacia and hyperparathyroidism.