Catheter-related hypersensitivity-type adverse reactions have been associated with insertion of the LANDMARK Midline Catheter (Menlo Care Inc., Menlo Park, CA). The authors' retrospective study showed an incidence for these reactions of 0.3% (7/2169) as well as an incidence of 3.3% (2/61) with insertion of CENTERMARK PICC (Menlo Care Inc., Menlo Park, CA), another aquavene-based catheter. The mechanism causing these reactions remains unknown, but the authors think that there is a small but significant risk of potentially life-threatening adverse reactions associated with insertion of these catheters. The health care professional who uses these catheters should be aware of these hypersensitivity reactions and should report any cases that occur to the Food and Drug Administration's MedWatch immediately.