The North American, Central American and West Indian species of the lichen genus Haematomma are revised, with special emphasis given to the chemistry and distribution of the taxa. Nineteen species and an additional variety are accepted for the region, including one new species from the West Indies: Haematomma caperaticum. All these taxa are given full descriptions, and a key to their identification is provided. The varieties of H. ochroleucum are regarded as unnamed chemotypes. The presence of fatty acids, including caperatic, rangiformic and bourgeanic acids, are reported for the first time for the genus and are taxonomically important. In addition, two new usnic/placodiolic-type dibenzofuran derivatives (Hgy-1 and Hgy-2) characterize a chemotype of H. guyanense, a common sorediate species known mainly from Florida. This species and H. leprarioides are reported as new to North America. Notes on the chemistry and, in a few cases, the morphology, of 11 non-American species are also provided. Rosellinula kalbii was found growing as a parasite on H. guyanense, the first report on this host.