Resin-modified glass ionomer cements (RMGICs) present several advantages (e.g. fluoride release), but their reported cytotoxicity has been associated with hydroxyethyl methacrylate (HEMA) monomer release. Therefore, different monomers were tested for use in RMGICs in order to improve their biocompatibility and reduce monomer release. Eight experimental liquid compositions were prepared replacing different percentages of HEMA (conventional monomer used in commercial RMGICs) with hydroxypropyl-methacrylate (HPM) and/or tetrahydrofurfuryl-methacrylate (THFM), which are known to have better biocompatibility. Moreover, two commercial materials (Fuji-Plus and RelyX) and two compositions, based on these (home), were included as controls. Monomer release of all materials (commercial, home and experimental) were tested using high-performance liquid chromatography (HPLC) methods after immersing discs in deionized-water (DW) or ethanol:DW. Cytotoxicity of the materials extracts was tested on normal human oral fibroblast line (NHOF-1) using 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. Three experimental materials containing THFM (F3, R3 and R4) showed less or similar monomer release compared to corresponding commercial products. Furthermore, two experimental materials (F3 and F4) showed similar effects on NHOF-1 cells compared to the negative control medium. The lower monomer release and higher cell viability of some experimental THFM compositions are encouraging. THFM partially replacing HEMA is potentially a suitable alternative for producing biocompatible RMGICs. Copyright © 2021. Published by Elsevier Inc.