HL7 is a huge undertaking and continues to grow. We talked about certain main themes of the spec that I've found interesting and thought you might too. You can always find additional information-especially from the HL7 website itself at www.hl7.org or www.altisinc.com/ IE/hl7.html. The main thing to remember is that HL7 is a specification for describing, formatting, encoding, and sharing of clinical and administrative data in healthcare. An easy way to remember that is that the 7 in HL7 refers to the Application layer in the OSI model. The next time someone talks about their HL7 software or application, you'll know that they really mean their HL7 compliant software or application. Then be sure to ask them how many composites are in their OBX segments!