Pros
Overall decent compensation package, work from home opportunities, intelligent coworkers. That is it. Everything else a con.
Cons
I literally feel like I have PTSD from this job. Every day (including weekends) I worked 10+ hours and was not infrequently in tears, for the first time in my career. I am not dramatic or inefficient so it was quite a shock to me coming from previous companies. Work life balance is nonexistant. You have to put in ridiculous hours and the company as a whole was tragically under staffed making it impossible to do your job adequately. Little useful training and clunky old systems that are frustrating to use are the norm. Very rigid corporate structure, email overload, annoying time tracking etc. Parexel will take on any study to the detriment of its employees, and the studies keep piling on.