Ribonucleic acid (RNA) and protein synthesis during myxospore germination were examined. When RNA synthesis was inhibited more than 90% by either actinomycin D (Act D) or rifampin, germination was prevented. The data were consistent with the interpretation that rifampin did not interfere with protein synthesis in any way other than by inhibition of messenger RNA formation. Act D concentrations as high as 20 mug/ml did not totally inhibit RNA synthesis. In the presence of 8 mug of Act D/ml, germinating myxospores synthesized transfer RNA, 16S RNA, and 23S RNA. Evidence was presented which indicated that messenger RNA was also synthesized early in the germination period both in the presence and absence of 8 mug of Act D/ml. One explanation for the escape synthesis of RNA in germinating myxospores is that Act D exerts a differential effect on the transcription of larger versus smaller cistrons, the latter having a lower probability of binding Act D. We have found that in the presence of 8 mug of Act D/ml, escape RNA synthesis in myxospores was 25% for 23S RNA, 55% for 16S RNA, and more than 90% for 4S RNA. We have shown that germination of myxospores requires both RNA and protein synthesis during the first 25 to 35 min in germination medium. This finding does not support the earlier suggestion by Ramsey and Dworkin that a stable germination messenger RNA is required for germination of the myxospores of Myxococcus xanthus.