N-terminal epitope tag - keep or remove ORF start codon - (Jan/13/2014 )

When adding an epitope tag to the N-terminus, should I keep the ORF's start codon or remove it? Obviously the true start codon will be before the epitope tag. I didn't know if removing it would cause issues or if it really doesn't matter either way. 

Thanks!

In theory you should remove it, so as to prevent ribosome skipping, but this is only the case for very short tags.  In practice I generally keep the initial ATG in my sequences, and haven't observed any problems.