I've balanced school and work/startup before - I launched a startup in undergrad, and worked at a corporation while doing my Masters. I think that if you are going to do two things which consume so much time and energy, that the most important thing is to make sure that your focus is the same for both. Then you get benefits on both sides. For example, I did my Master's thesis while I was a product manager, and the thesis was related to the product. This meant that my knowledge from work informed my research, and I could go far more in depth into questions about product behavior than a product manager could normally spend time on.<p>So, if your startup and your dissertation are focused on the same basic problem, then it's not really splitting your focus, but it is adding more "to-do's" to your list. The hard part with a startup is finding a way to get all those to-do's done in limited time and money. This is always a challenge, just realize that school is going to take time away and budget time and money accordingly. For example, if you could do something for your customers in a month without school, maybe you should not promise anything in less than 3 months. If you don't budget time appropriately, you will need to ship something the week before finals, and something's got to give.<p>Of course, if you do this, watch out for intellectual property issues with your school. Depending on your school and what you are doing, this may or may not be an issue. Usually, you can talk to the school's commercialization office, and they have a process for evaluating whether the school has an interest. You might think it's better to fly under their radar, but using the process grants you either a) institutional support, which is great, or b) a declaration that the school doesn't have an interest, which is also great.<p>If you don't already kind of know what you want to do for your dissertation and/or startup, then you aren't ready. For either, really. Do not attempt either a startup or PhD, and especially not both, without some passion. If they're not both the same passion, and you feel more for one than the other, then you already know what your decision should be. This isn't meant to be harsh, just as advice.<p>A startup can be a way to get around the issue of having your ideas get stuck in academic neglect. However, be aware that there are downsides to trying and failing. The academic route is long and not glamorous, but you are also unlikely to end up living in a car with your significant other leaving you. That is a possibility with failed startups, if you let it be (trust me on this). Have an exit strategy for if it doesn't work out. If academics is your plan B, make sure you keep publishing and retain your contacts in the academic world.