The need for procedural sedation is extensive and on the increase in numbers of patients. Minor treatments or diagnostic procedures are being performed with inadequate sedation or even without any sedatives or analgesics. Also, sedation techniques that support advanced, high-quality, in-patient care procedures representing easy performance and rapid recovery are requested for increased effectiveness. In this doctoral thesis, patient-controlled sedation (PCS) using propofol and alfentanil for surgical and diagnostic procedures was studied. The overall aim was to study aspects of safety, procedural feasibility and patients’ experiences. The main hypothesis was that PCS using only propofol is a safe and effective method for the induction and maintenance of moderate procedural sedation. The studies included were prospective, interventional, and in some cases, randomized and double-blinded. Data on cardiopulmonary changes, level of conscious sedation (bispectral index and Observer’s assessment of alertness/sedation [OAA/S]), pain, discomfort, anxiety, nausea (visual analogue scales), interventions performed by nurse anaesthetists, surgeons’ evaluation of feasibility, procedure characteristics, recovery (Aldrete score) and pharmacokinetic simulation of concentrations of drugs at the effect site supported the analysis and comparison between PCS and anaesthetist-controlled sedation and propofol PCS with or without alfentanil. PCS can be adjusted to cover a broad range of areas where sedation is needed, which, in this thesis, included burn care, gynaecological out-patient surgery and endoscopic procedures for the diagnosis and treatment of diseases in the bile ducts (endoscopic retrograde cholangiopancreatography [ERCP]). PCS for burn wound treatment demands the addition of alfentanil, but still seems to be safe. PCS was preferred by the patients instead of anaesthetist-controlled sedation. The addition of alfentanil to PCS as an adjunct to gynaecological surgical procedures also using local anaesthesia increases the surgeon’s access to the patients, but impairs safety. Apnoea and other such conditions requiring interventions to restore respiratory function were seen in patients receiving both alfentanil and propofol for PCS. Patients’ experiencing perioperative pain and anxiety did not explain the effect-site concentrations of drugs. Different gynaecological procedures and patients’ weights seemed to best explain the concentrations. For discomfort and pain during the endoscopic procedure (ERCP), propofol PCS performs almost the same as anaesthetist-performed sedation. Overall, as part of the pre-operative procedures, PCS does not seem to be time-consuming. In respect to the perioperative perspective, PCS supports rapid recovery with a low incidence of tiredness, pain, and post-operative nausea and vomiting (PONV). The data suggest that PCS further needs to be adapted to the patient, the specific procedure and the circumstances of sedation for optimal benefit and enhanced safety.