Infrared speckle interferometry combines the full resolving power of large telescopes with high photometric sensitivity over the wavelength range 2.2 to 12 microns. Despite improved atmospheric seeing at these wavelengths, seeing fluctuations limit measurement precision. Astrometric companions have been detected with angular separations ≥0.1 arcsec and magnitude differences ≤3.7 mag. Results illustrate seeing limitations and show how the usual position angle ambiguity can be overcome. These measurements yield masses and absolute magnitudes for calibrating the lower main sequence. In some cases, orbital motion is detected. A method of “shift-and-add” enables detection of substellar (0.04 to 0.08 M⊙) companions. Future improvements involving detector arrays and seeing monitors are discussed.