The present room temperature curing composition comprises an organopolysilethylenesiloxane represented by the following general formula: ##STR1## wherein R.sup.1 to R.sup.4 each represent an alkyl having up to 8 carbon atoms or a phenyl group and n is an integer of 10 or above, and an organosilane or an organosiloxane having two or more hydrolyzable groups such as alkoxy groups in the molecule. The composition can form a cured product high in rubber strength and excellent in chemical resistance.