The characterization of industrial slurries and emulsions has traditionally relied upon off-line measurements of particle size and shape. Recent advances in sensor technology have made it possible to implement in-line particle characterization on a number of industrial processes, including comminution, crystallization, and emulsification. This paper presents several recent applications of two in-line instruments developed in our laboratory: an ultrasonic instrument used to monitor particle size in slurries during milling operations and to determine droplet sizes in emulsions, and a new in-line video camera for observing the morphology of crystals produced in a commercial process.