Knowing various types of systematic, and unsystematic, linguistic errors and identifying the reasosns and origins of the errors enable language instructors and textbook writers to adopt a more informed approach to teach a second language. Knowledge of such errors can be developed through conducting field and applied research. Studies on teaching English as a second language in other languages using "contrastive linguistics" and "error analysis" have proved promising. However, in teaching Persian to nonnative-Persion speakers, either there has been no systematic research, or research in this area has not yielded important results for teaching Persian. Studies in this area have been primarily limited to frequency counts and tallies.Five stages usually need to be followed when error analysis is used: identification of linguistic errors, classification of errors, description of errors, quantitative and qualitative analysis, and provision of pedagogic and research implications. Unfortunately, the majority of studies on error analysis on Persian have followed only the first three stages. The last two stages in error analysis are particularly important if the primary aim of error analysis is to help nonnative-Persian speakers. Finding answers to questions for language researchers is more important than merely analyzing language errors quantitatively. What leads to linguistic errors among language learners speaking different mother tongues?, Do errors help nonnative-Persion speakers learn Persion, or do such errors prevent them from learning it?, how can errors be prevented?, and what errors should be corrected when they occur?, who should correct the errors: language teachers, language learners, or classmates?, who should start correcting the error and who should end it?, when and how should the errors be corrected in teacher-centred and learner-centred classes?, and how should errors related to skills and compoenets be corrected? are the questions language researchers need to look for solutions.I hope that researchers will use error analysis to analyse linguistic errors and arrive at some useful pedagogic implications for language learners.