‘Health Equipment Information’No. 128 (October 1984) contains the results of the UK Health Departments’evaluation of ultrasonic humidifiers—the study was directed by Dr B. Hayes and Mr S. Tilling of Dudley Road Hospital, Birmingham, UK. The humidifiers involved were the DeVilbiss 35B and 65, the Intersugical Variosonic, the Medap Monsun 803 and the Mistogen EN145(E). A previous‘HEI’(No. 103) looked at single-use unheated humidifiers; a future report will include evaluations on heated vapourizing humidifiers: the Chemetron Midi, the Draeger Aquapor, the Fisher&Paykel 328 and 418, the Penlon Model H and the Puritan Bennett Cascade II.For full details of the evaluation findings, readers should consult‘HEI’128–the following contains extracts from the report.Enquiries about the evaluation of humidifiers should be directed to Gordon Judge, Scientific and Technical Branch, DHSS, 14 Russell Square, London WC1B 5EP.