I taught 4 types of EFL courses to undergraduate students online: Grammar, writing, culture and study skills using Blackboard and Nicenet. Online instruction was used as a supplement to traditional in-class instruction. Significant differences were found between pre- and post-test scores in writing, grammar and culture but not in study skills. The achievement level was higher among active participants who posted threads and shared in the discussion than passive participants who were just browsers and did not write anything, and between members of the latter group and those who were not registered in the online courses at all. The effect of online instruction on students' attitudes is also reported. (Contains 2 tables.)