Purpose.To determine the levels ofAcinetobacterspecies associated with normal soft contact lens wear and to determine whetherAcinetobacterspecies are involved in adverse reactions that occur during contact lens wear.Methods.Patients wore soft contact lenses on an extended-wear basis. The bacteria on lenses and ocular swabs during asymptomatic and symptomatic lens wear were identified using standard microbiologic methods.Results.Acinetobacterspecies were isolated and identified from 16 (13%) of 126 patient samples. Greater numbers ofAcinetobacterspecies were isolated from lenses of patients experiencing adverse responses than from asymptomatic patients.Acinetobacterspecies were isolated from patients experiencing symptomatic adverse responses in 4 (13%) of 32 cases.Conclusion.It appeared thatAcinetobacterspecies colonized the eye of extended contact lens wearers at a time when the normal functioning of the eye was compromised by contact lens wear. WhenAcinetobacterspecies were in high numbers on a contact lens, an adverse response occurred. This may implicateAcinetobacterspecies as a contributing factor to adverse responses associated with contact lens wear.