Diagnostic ultrasound may be used to assess the suitability of patients for percutaneous dilatational tracheostomy (PDT) in the intensive care unit (ICU). It may identify patients unsuitable for PDT, prevent puncture of aberrant vessels, estimate the distance from the surface of the skin to the trachea, and ensure accurate placement of the needle in the trachea. We conclude that diagnostic ultrasound permits careful evaluation of patients for whom PDT is being considered, and adds to the safety of the procedure.