These days, hea hhcare services are enjoying the applicat ion of pervasive computing systems.rnAdvances in wireless tec hnologies- such as intelli gent mobile devices and wearable networksrncan improve communication among patients. physicians, and other healthcare workers as well asrnenable the delivery of accurate medical information anytime anywhere, thereby reducing errorsrnand improving access. However, transmiss ion of vital signs, frequency of tran smi ssion of vitalrnsign s, network communication cost, context refinement, and management of large contexts arernstill problems of pervasive hcalthcare systems. In this work, we propose a co ntext awarernpervasive healthcare system for HIV!AIDS (I-Iuman Immunode ficiency Virus! Acq uiredrnImmunodeficiency Syndrome) patients (CAPHS). The architecture of the system consists ofrnthree constituents: the patient unit, the healthcare unit and the doctor/nurse un it. The pati ent unitrnconsists ofa group of body sensors for detectin g vital signs data from patients and transmitting itrnto the patient's smart phone via Bluetooth. After preprocessing, the smart phone transmits vi talrnsigns context information to the heahhcare un it via Internet for further processing and reason ingrnif there is any abnorma lity. This preprocessing helps to determine the frequency of transmi ssionrnof vital signs and reduces the network communicat ion cost to transmit vital sign data. At thernsame tim e, it a lso increases the effic iency of the healthcarc unit because this operation reduces itsrntask of context refinement. The hea lthcare unit is rich in ART (Antiretroviral Thera py) ontologyrnknowledge that we developed. For better management of large contexts, we usc a hybrid contextrnmanagement approach in which the high level schema ontology stored in OWLlRDF (WebrnOntology La nguage/Resource Description Framework) format and the ontology in stances storedrnin ordinal)' relational databa se. The doctor/nurse unit is the thinnest of all units in terms ofrnnumber of components. It communicates with the health care unit via InternetiSMS so thatrnphysicians can remotely monitor their pat ient. We have developed a prototype implementationrnfor the system and we see that it is promising.