Hello – This is Ellen from Dr. Pacik’s office… The panties do not have to be “tight”just simply snug. Many of the girls wear regular bikini or brief panties and some even wear boy shorts. As long as they fit snugly and have some type of full cut to them to be able to wear a feminine pad while dilating the first few days is okay. If they are too tight you may be uncomfortable but if they are too loose and baggy then it will be difficult to hold everything in place. Thong or g-string panties are not recommended due to the skimpy cut, especially in the crotch area. They tend not work as well or be as comfortable. No need to buy swim suit bottoms or anything tighter than normal snug undies. You may also want to keep in mind dilating in the beginning can be a little messy, so you may not want to wear anything filly or lacy. Cotton or cotton blends are comfortable and also allow for breath-ability. I hope this helps. Please feel free to call me or e-mail me if you have additional questions. ellen@plasticsugerypa.com