How do I delete rows in a data frame?

I have a data frame named "mydata" that looks like this this:

   A  B  C   D 1. 5  4  4   4 2. 5  4  4   4 3. 5  4  4   4 4. 5  4  4   4 5. 5  4  4   4 6. 5  4  4   4 7. 5  4  4   4 

I'd like to delete row 2,4,6. For example, like this:

   A  B  C   D1. 5  4  4  4 3. 5  4  4  4 5. 5  4  4  4 7. 5  4  4  4