The term “Long Covid”- coined by patients with unexplained sequelae of Covid-19 first appeared in summer 2020, to describe a new medical condition, produced by a new pathogen. My talk will follow a much longer history, that of “medically invisible conditions”, that is, those devoid of objective disease signs, or, in today’s terms, biomarkers. A patient, often a woman, reports multiple, debilitating, and frequently oscillating symptoms. Her physician orders a long battery of tests to find out what is wrong. All the results of these tests are normal, but the patient continues to report distressing symptoms that fail to be alleviated by standard medication. At that point, she may be described by professionals as suffering from a “medically invisible disorder”: the impossibility of translating the patient’s subjective symptoms (illness) into objective signs of a known disease. Not infrequently, people with “medically invisible disorders” are told that their condition is not a “real” – that is, biological- disease and that it originated “in their head.” The denial of the biological reality of their illness may lead to psychic misery, social isolation, and stigma. My talk will follow the history of a few “medically invisible disorders”: chronic fatigue syndrome, fibromyalgia, “chronic Lyme”, and multiple chemical sensitivity. The history of a new condition, Long Covid, was and continues to be shaped, I’ll argue, by the convoluted past of other, akin disorders.