The article concerns the further history of religious discourse between the Silesian-Prussian Schwenckfeldians and Lutherans after 1529 in Prussia, other reformation circles joined in it as well. The arrival of duke Fredrick von Heydeck, a close political associate of Albert of Prussia, in the Legnica duchy in 1529 happened at an important stage. While in Silesia, Heydeck adopted the Schwenckfeldian spiritualism and, upon his return to Prussia in 1530, he arrived with Schwenckfeldian clerics, inviting them to take over parishes of his counties, Lötzen and Johannisburg in Prussia. That caused a vivid reaction of Pomesania bishop Speratus, who in June 1531 summoned those clerics to the Synod at Rastenburg for the purpose of asking them questions about the principles of their faith. Some of them, such as Peter Zanker and Georg Landmesser, put their declarations of faith in written form. In December 1531 duke Albert summoned both the most important among the Lutheran clergy and the key followers of Prussian Schwenckfeldian spiritualism. The latter were supported in the issue of the Rastenburg meeting by a cleric from Legnica, Fabian Eckel. Due to Duke Albert’s refusal to publically condemn the Schwenckfeldians, bishop Speratus was not pleased with these talks. He requested Martin Luther’s intervention. In 1532 he sent a public letter to the duke. This provoked a response from the clerics of Zurich, who joined in on the religious dispute in Prussia, sending Albrecht a letter-treaty from Heinrich Bullinger. The Schwenckfeldian movement in Prussia started to die out in 1535. Among the reasons were Heydeck’s death and change in duke’s religious policy, resulting from mounting internal difficulties relating to the political consolidation of the Prussian states.