In biological research it is often desirable to rear and handle animals free from microorganisms. This is particularly true in nutritional studies in which it is generally recognized that certain orgnisms in the digestive tract can supply nutritional factors which might otherwise be lacking in the diet. The possibility of this intervention makes it necessary to devise techniques for rearing and handling insects aseptically, in so far is the fauna and flora of their intestinal tract and of their environment are concerned. Consequently, a technique used throughout the present series of studies was developed making use of specially designed equipment by means of which nymphs of the cockroach, Blattella germanica (L.), were hatched and maintained under aseptic conditions, fed aseptic food, and kept aseptic throughout a series of measurements to evaluate their weight increment. The equipment and methods used constitute the basis of the present paper.