title: Barriers to the acceptance of in vitro alternatives.
abstract: Despite a considerable effort by the scientific community over many years, the replacement of traditional animal tests by in vitro alternatives has not yet been achieved. Why are in vitro alternatives not more widely accepted by scientists and regulators? Barriers to acceptance, both overt and covert, must be recognized and surmounted if further progress is to be made. At least seven barriers to acceptance of an in vitro method will be discussed.
  
  
  RESULTS
  has it been adequately validated? Scientific: is it based on good science? Legislative: can it replace an OECD Guideline?
  
  
  METHODS
  has it been developed in another laboratory? Psychological: will it make traditional skills redundant? Litigation: will it stand up to legal scrutiny in court? Regulatory: will regulators modify their traditional hazard assessment criteria?
authors.affiliation: Environmental Safety Laboratory, Unilever Research, Sharnbrook, Bedford MK44 1LQ, UK.
authors.forename: D G
authors.initials: DG
authors.lastname: Clark