The efficacy, with respect to preventing i.v. catheter damage, of creating a skin entry site by first piercing the skin with a large gauge needle through which an over-the-needle teflon catheter is then placed was evaluated. In 50 adult volunteers two 22-gauge i.v. catheters and two 24-gauge catheters were placed through the forearm skin into the subcutaneous tissue. One catheter of each size was placed through an entry site created by piercing the skin with an 18-gauge disposable, stainless steel needle. One catheter of each size was inserted through nearby skin without creation of an entry site. Two to three weeks after insertion all catheters, along with 50 catheters of each size that had not been inserted, were examined under a microscope for evidence of damage. Intravenous catheter damage was more prevalent in the 24-gauge catheters than the 22-gauge catheters (P less than 0.05). No differences in frequency of damage were noted for either gauge catheter inserted through an entry site compared with those inserted without a prior skin puncture. Twenty-four-gauge catheters, but not 22-gauge catheters, placed into the subcutaneous tissue were damaged more frequently than were catheters that had never been inserted (control catheters). This study demonstrated that 24-gauge catheters are more likely to be damaged during insertion into the subcutaneous tissue than are 22-gauge catheters. We also demonstrated that creation of a skin entry site by piercing the epidermis with a needle of larger gauge than the catheter to be placed is not efficacious in preventing intravenous catheter damage during insertion.