ABSTRACT
The substrate preferences of the lichens known from Maryland are listed and discussed. Substrate reversal is noted in <em>Alectoria</em>, <em>Cetraria</em>, <em>Hypogymnia</em>, <em>Parmeliopsis</em>, and <em>Umbilicaria</em>. Most of the species grow on deciduous trees; saxicolous species occur mainly on acidic rocks. State records are cited for 92 species.