  Macroscopic fundamental and Dirichlet strings have several potential
instabilities: breakage, tachyon decays, and confinement by axion domain walls.
We investigate the conditions under which metastable strings can exist, and we
find that such strings are present in many models. There are various
possibilities, the most notable being a network of (p,q) strings. Cosmic
strings give a potentially large window into string physics.
