The iliac crest is the only site at which aspiration and biopsy may be safely performed in an adult.¹ The posterior superior iliac crest (as shown below) is the preferred site for aspiration, because this site decreases the risk of pain, increases accessibility, and isn’t near any vital organs or vessels.¹ The patient should be placed in the lateral position with one leg flexed, or in the prone position.^1,2 The practitioner may use the anterior iliac crest with a patient who can’t lie prone, or when the posterior iliac crest is unapproachable or not available because of infection, injury, or morbid obesity.¹ This location is generally not preferred because its dense cortical layer, which makes obtaining specimens more difficult, necessitates smaller specimens, and increases the risk of pain.