Subject: Does active transport ONLY occur against a concentration gradient?

I am reviewing some science questions, specifically "Which statement is true 
about active transport?"  The correct answer is "it occurs against the 
concentration gradient." Fair enough, but an incorrect answer is "it occurs 
with the concentration gradient."  I'm not sure if this is necessarily wrong. 
Although active transport isn't necessary when moving toward the gradient, what 
would prevent it from occurring in either direction (efficiency?)

Re: Does active transport ONLY occur against a concentration gradient?