We present measurements of the thermal expansion of the glass forming alloys Zr57Cu15.4Ni12.6Nb5Al10, Zr65Cu17.5Al7.5Ni10, Zr11Cu47Ti34Ni8, Zr60Cu18Al10Ni9Co3, Pd78Cu6Si16, and Pd82Si18 in the melt and the undercooled state in the TEMPUS facility under microgravity conditions. The samples were imaged with a high-resolution charge-coupled device-camera with on-board recording. After the mission, the video tapes were analyzed by digital image processing. The volume was found to be a linear function of temperature in the temperature range investigated. The thermal expansion coefficients in the melt and the undercooled state are between 5.5×10−5 and 7.9×10−5 K−1. The volume increment at the melting point was between 1% and 2.1%. Phase separations could be observed by a change of the slope of the volume versus temperature curve. The thermal expansion data can be interpreted qualitatively in terms of the free volume model. © 1999 American Institute of Physics.