Previous experiments in space (unmanned satellites, space shuttle and the International Space Station, ISS),have shown that adult Drosophila flies change their motile behaviour in microgravity. A consistent increase in motility in space was found in these experiments, but mature flies (two weeks old) showed less increase than recently hatched flies. In the case of relatively long exposure to microgravity, the aging of male flies measured upon return to Earth was increased, with flies dying earlier than the corresponding in-flight 1g centrifuge or ground controls. The older flies, which experienced a smaller increase in motility, did not show this acceleration in the aging process. More recently we have performed comparative experiments using ground simulation facilities. Preliminary experiments using a random positioning machine (RPM) indicate that the effects of this simulation approach on the behavior of Drosophila are of smaller magnitude than the corresponding exposure to real microgravity. Further experiments are in progress to confirm this effect. However, when exposed to magnetic levitation, flies exposed to simulated weightlessness increased markedly their motile behavior compared with 1g controls both inside and outside the magnet. This altered gravity-related increase in motility was also less pronounced in more mature flies. This motility effect at the levitation position reproduces the results in real microgravity indicating the interest for space science of this simulation approach. Similar experiments are being performed in the Larger Diameter Centrifuge (LDC) located in ESTEC (the Netherlands) and indicate that 6g, 12g and 20g are key points in the hypergravity response in flies. Our experiments have shown that developmental processes from embryo to adult proceeded normally in the magnet, the RPM and the LDC. In terms of gene expression, preliminary results indicate that the affected set of genes under hypergravity responds in general in an opposite direction than that induced by the real or simulated microgravity exposure. The interest in conducting comparative parallel experiments in the complete spectrum of ground simulation methods is shown in the above studies and will be achieved in the near future.