AbstractSilencing of a target-genes by small interfering RNA (siRNA) has emerged as a powerful new tool not only for basic research but also with potential therapeutic benefits. This paper demonstrates that optimal delivery strategy is crucial for effective target-gene silencing. Using lipofection, under defined conditions, we were able to markedly down-regulate expression of the selected genes involved in rhabdomyosarcoma metastasis: MET, CXCR4, LIFR and PAX3-FKHR.