As one of the best candidates for simulating the microgravity conditions in space, low gravity environments provided by applying an upward magnetic force have been considered to grow protein crystals. Since 2002, the stable and longtime durable microgravity generated by a superconducting magnet has been available for protein crystal growth. In this paper, for the first time, we grew protein crystals (orthorhombic lysozyme crystals) at quasi-microgravity. The present study showed that quasi-microgravity improves the crystal quality effectively and reproducibly. The application of strong magnetic field also improves the crystal quality. Furthermore, it is possible to know if microgravity is effective for the improvement of crystal quality or not by growing crystals in microgravity and hypergravity inside the superconducting magnet and comparing the crystal quality with each other. Such test will be useful to select promising proteins prior to the space experiments. (C) 2004 Elsevier B.V. All rights reserved.