The aim of this study was to investigate the effect of an integration of flooding and enhancement input program on the acquisition of grammatical structures of first year preparatory school students. The participants were sixty students. They were randomly assigned into a treatment group and a non-treatment group (30 students each). The instruments of the study included: a test in vocabulary items. The treatment group was taught using the integration of flooding and enhancement input program while the non - treatment group was taught following the plan of the Ministry of Education in Egypt. The participants were pre and post tested. Results revealed that the integration of flooding and enhancement input program had positive results. Suggestions for further research were presented.