Kerosene sprays containing extracts of pyrethrum gave a high kill of adult [female] Blatella germanica when applied by a settling mist method at certain concs. and dosages. The majority of the insects dropped their oothecae prematurely, possibly because of muscular contractions induced by the pyrethrins. Comparison of the % hatch of oothecae so detached with that of oothecae manually removed from untreated [female][female], showed that the pyrethrins exerted some insecticidal action on the oothecae, but that the % mortality of oothecae was less than that of the [female][female] to which they had been attached. When a high kill of [female][female] is obtained by pyrethrum sprays, the [female][female] are evidently more susceptible to this insecticide than are their oothecae. With the possible exception of the large nymphs, the ootheca is the most resistant stage of the German cockroach to pyrethrum sprays. The effect of the pyrethrins on [female][female] and their oothecae was compared with that of other toxicants. At any unusually high conc. normal butyl carbitol thiocyanate gave about the same % mortality of [female][female] and oothecae as did the pyrethrins, but did not cause the [female][female] to drop their oothecae, although its paralytic effect was greater than that of the pyrethrins. This thiocyanate evidently had some insecticidal value against the oothecae at the conc. used, but the [female][female] were more susceptible than their oothecae. At the concs. used, cresylic acid was comparable to the thiocyanate and rotenone to the pyrethrins. Neither substance caused the [female][female] to drop their oothecae and neither killed the [female][female] or their oothecae. Oothecae manually detached from [female][female] shrivel rapidly under room conditions, but a shrivelled ootheca may hatch completely or partially, even when removed from the [female] soon after it is extruded. A better hatch is obtained by keeping detached capsules in contact with physiol. salt soln., thus preventing shrivelling by simulating the condition of liquid transfer existing when the ootheca is normally attached to the [female]. Early removal of an ootheca accelerates production of the succeeding ootheca.