Gigi, I think it took several weeks or even a month before I noticed a difference in my eyebrows. I would check MakeupAlley.com for reviews of castor oil to see what most folks said. Initially, I used it for my eyebrow tail which is fine now. Then, I decided I wanted more hair on the area of my brows closer to my nose. That seems to be taking longer maybe because it involves more hair but I AM noticing some difference.
Second note: I suffer from systemic sclerosis, aka scleroderma, which seems to have affected my hair follicles. I've lost most hair on my fingers and toes, arms, legs, and armpits. My head, lashes, and brows seem not to be affected, but who knows?