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Informal fallacies of argumentation as pitfalls of reasoning appear frequently in students' written texts, specially EFL / ESL Learners' argumentative essay writings. The present study examines whether gender could be considered as a determining factor influencing Iranian advanced EFL learners' argumentative writings with regard to informal fallacies of argumentation. The corpus comprised of argumentative essays written by 120 Iranian male and female English language learners. The participants’ age and discipline were also included as independent variables. Nine major categories of informal fallacies were examined in learners’ texts and the observed frequencies were analyzed using MANOVA. The results of the Multivariate Tests for all independent variables and /or their interactions indicated no significant differences for the overall informal fallacies. However, three separate instances of differences were observed. Finally, the findings of the present are discussed in relation to the previous literature and some implications of the study are suggested.