Most of the damage done by insects to grain in storage and shipments is brought about by four species. These are the granary weevil, the rice or black weevil, the lesser grain borer or Australian wheat weevil, and the Angoumois grain moth. Other species or groups of species described in this bulletin can cause great damage to grain if storage conditions are unusually favorable for their increase. Yet if grain in the unbroken kernel remains unaffected by the four insects mentioned, it is not likely that any other insect will damage it appreciably in commercial storage or shipments, except for the khapra beetle which at present has a limited distribution. The secondary pests discussed herein are for the most part surface feeders in both adult and larval stages. Some may eat their way into kernels of grain and lie hidden there; most of them are found feeding upon grain dust or broken surfaces of kernels exposed either by mechanical injuries to the grain in handling or by the feeding of the four primary grain pests with which they are usually associated. They can therefore be largely removed by grain-cleaning operations. With the exception of the lesser grain borer, the larvae, or grubs, of the primary pests mentioned are not ordinarily capable of a free existence outside the kernel. They live entirely within the kernel, where they feed unseen and usually unsuspected. They cannot be removed by ordinary cleaning machinery and must be controlled by other means. Methods of preventing infestation of grain are discussed briefly.