See if these two webpages help? http://chinese.stackexchange.com/questions/1263/what-is-the-difference-between-y%C7%90qi%C3%A1n-%E4%BB%A5%E5%89%8D-and-zh%C4%ABqi%C3%A1n-%E4%B9%8B%E5%89%8D http://www.italki.com/entry/127844 From my personal experience, 之前 is like "prior to, before" while 以前 is more like "ago, past" For example: 在我走之前 before I go. Even though, you can use 以前 in this case as well. I personally find 之前 more natural. 很久以前 long time ago. Even though... 很久之前 works too.. (._.) arg, I think I am not helping much.

1) "之前 = 之（pron)+ 前"，the antonym of it is "之后=之+后” you can understand it as "before something happened" and "before some time passed". as well. 2）以前“ normal just used as " before some time " , the relative term of it is " 以后” ex: it's better wash your hands before eating 吃饭之前，最好先洗手。or 吃饭以前，最好先洗手。 all the thing i have told you was truth. 之前我跟你讲的都是真话。or 以前我跟你讲的都是真话。 but something different in some situation as below 1) long time ago... / long long time ago... : 很久以前... / 很久很久以前... before starting with a fale story, normally the term " 以前“ is used to emphasis some far-off times and mystery feeling. 2) if you should use "before" or "after" together, it's better use them in symmetric way. ex. 之前..., 之后... or 以前..., 以后...

以前=long time ago 之前=before sometime 我以前在北大上学。 我之前来过这。