Does Opti-mem contain serum - (Oct/19/2014 )

It says reduced serum, which to me means it contains a little serum.  

Hi, IIRC the expression "reduced serum" means the OPTIMEM medium is optimized for growing cells with adding a reduced amount of serum as compared to "normal" media, so I think OPTIMEM itself is actually serum-free.

Never worked with it, so please someone correct me if it's wrong.

I don't think it does. I will second what Tabaluga said. It's serum free but allows the 50% reduction.