Although new technologies such as array genomic hybridization to diagnosis the cause of intellectual disabilities (ID) are exciting to clinicians, the value of an etiological diagnosis to the families of affected children is largely unknown. Parents of 20 children with ID, 10 with and 10 without a causal or an etiological diagnosis were interviewed in depth about the value they place on such a diagnosis. They were asked about experiences acquiring services, use of support groups, interactions with family and friends, and opinions on prenatal diagnosis. Parents were also asked whether their child's diagnostic status had influenced these events or affected the couple's reproductive decisions. Finally, parents were asked whether their interest regarding the importance of an etiological diagnosis had changed over time. Interview transcripts were analyzed to determine values parents place on etiological diagnoses and comparisons were made between the two groups. These parents felt the need for a diagnosis most intensely when developmental concerns were first noted, and most parents agreed that this intensity diminished over time. All would have preferred to have an etiological diagnosis, but for some the only reason was curiosity. Validation was the most important value attributed to a diagnosis: it offered legitimacy for the child's behavior and appearance. However, a descriptive label, such as autism, was often more useful to parents than a rare but specific etiological diagnosis. Surprisingly, between the two groups there were no differences in the parents' perceptions or experiences related to the presence or absence of an etiological diagnosis for their child's ID. © 2009 Wiley-Liss, Inc.