Weaning from mechanical ventilation is attempted when the patient's underlying condition has resolved and when the patient is able to maintain cardiovascular and respiratory stability within normal parameters. From a medical perspective, when to wean is based on patient readiness determined by objective, physiological criteria. Psychological readiness is equally important, yet criteria determining psychological readiness is generally omitted from the list of ready to wean parameters. Reasons for this may be that psychological readiness is difficult to measure and is based upon subjective opinions. Nursing research exploring critical care nurses' and patients' experiences of weaning has extended knowledge concerning patients' psychological readiness to wean. From examination of this research, three important criteria emerge. It is recommended that the addition of these criteria to the list of physiological criteria will not only achieve a holistic assessment of patients' readiness to wean, but will also acknowledge the important and complementary role of the nurse in the weaning process.