If I have a Bachelor's of Science degree from a 4 year university not in computer science, but I want to get a Master's in computer science, what are my steps/prerequisites? Do I need another undergraduate degree in computer science?

First you ABSOLUTELY SHOULD NOT attempt to earn a second undergraduate degree, this would be a waste of time and money. Second you need to deeply examine why you think you want a Masters degree in CS and what you hope to do with this degree -- the vast majority people employed in the broad field of information technology DO NOT HAVE Masters degrees. A Masters Degree in CS further will likely NOT prepare you for any true research in Computer Science nor will it prepare you for teaching Computer Science. It is somewhat valued by large buecratic organizations that have a pay scale that rewards degrees but work in such organizations is both harder and harder to find and very likely NOT what most young people aspire to these days... I would strongly suggest investigating the programs offered to people in your situation -- folks with NO background in computers that are considering going back to school to earn a Masters. One of the better such in person programs: http://csmasters.uchicago.edu/ Here are two well regarded online programs: http://www.omscs.gatech.edu/ http://www.drexel.com/online-degrees/engineering-degrees/ms-cs/index.aspx Good luck!