From what I read and heard, the day before the test — the prep day — is the worst part, and the actual procedure is not a big deal. I was instructed to take four litres of Klean-Prep mixed with water, a lemon-lime drink, or some other clear (ie. non red or purple) liquid. I was to start at 2:00 pm on Tuesday, but they said if you have trouble drinking large amounts of liquid (and four litres is about the size of two large party-sized pop bottles), you could start earlier. I planned to start at 12:00 pm, and I was supposed to drink a cup (1/4 litre) every ten minutes.