We discuss visibility data and its analysis for 15 late-type stars observed with the U. C. Berkeley Infrared Spatial Interferometer (ISI). The ISI is a two-element heterodyne interferometer operating in the 9- to 12-micrometers wavelength region and is located at Mt. Wilson. Visibility curves were calculated using a radiative transfer model and compared with the visibility data from the ISI. A (chi) 2 fitting procedure has been used to estimate the inner radii of the dust shells, optical depths at 11 micrometers , and the temperature at the inner radii. For stars in which the dust is completely resolved estimates of the stellar diameter and temperature can also be made. We present preliminary visibility data for the stars NML Cyg and IRC +10420 obtained recently using a 10-m baseline. In addition, we present preliminary recent data and analysis for the six stars, alpha Ori, omicron Cet, IRC +10216, R Leo, VY CMA, and R Aqr using a 32-m baseline. The visibility data for alpha Ori covers a sufficient range of spatial frequencies to make a determination of its diameter. Within a 95% confidence interval we obtain a diameter of 0".053+/- 0".003. For the other stars the recent 32-m baseline data are compared with previous models and further constrains some of their parameters.