Physical symptoms and the attributions assigned to them are fundamental aspects of individuals' illness representations and influence health behaviours. The effects of the presence or absence of symptoms and the interpretation of these symptoms on the initiation of HIV testing and medical care are explored using data from a psychosocial study of HIV illness in late middle-aged and older men and women. The absence of symptoms negatively influenced willingness both to seek testing and to seek medical care. While the presence of symptoms would be expected to lead to testing and the initiation of medical care, the effect of symptoms was dependent on causal interpretations of the symptoms. Symptoms attributed (or misattributed) to other illnesses or to normal aging did not lead to initiation of testing or care. These results appear to be due to people's lay belief that illness must include symptoms and due to a resistance against accepting an illness identity. This research suggests that HIV education and counselling should emphasize the need for individuals at risk for HIV to seek testing and medical care even if symptoms of the disease are absent.