This report describes the application of hot embossing to produce parts with microstructure. An embossing machine, designed for microfabrication, was used to emboss PMMA and PC substrates. An insert with micro-holes of various diameters was applied in the hot embossing experiments. Effects of process parameters, such as embossing temperature, embossing force, embossing period and demolding temperature, on replicated heights were studied. Results show that replicated heights on smaller holes are smaller. Embossing temperature is the most important factor. Demolding temperature hardly affects the replication ability. Replicated heights increase with embossing period. The height can reach a very high value with a large enough embossing period.