18 volunteers of our Faculty participated in two quasi-identical experiments six months apart. Repeated measurements of reaction time and synchronicity of peak forearm EMG values during bimanual reactions are analyzed by means of analysis of variance with subjects and measurement period as factors. Using Ebel's formula, test-retest reliabilities derived from the analysis vary between .82 and .94 for reaction times on different tasks and conditions and between .75 and .92 for synchronicity of peak EMG values.