Traditional teaching of intramuscular injection technique is that the plunger is aspirated prior to injection to ensure that the needle isn’t intravascular. However, this practice is associated with increased pain and there is a lack of scientific data demonstrating its necessity. Ipp and colleagues conducted a clinical trial in 113 healthy 4-6 month infants and compared two injection approaches for DPTaP-Hib immunization: 1) slow aspiration, injection, and withdrawal vs 2) no aspiration and rapid injection and withdrawal (Arch Dis Chil 2007; 92:1105-8). They found no adverse events in either group, but also found that use of the no aspiration and rapid injection and withdrawal approach was much better tolerated. Current recommendations support the use of this technique for immunization of infants. However, to my knowledge the safety of injection without aspiration hasn’t been evaluated in other age groups, or with other vaccines and medications.