In September 1967 a Symposium on Neurobiology of Invertebrates was held at Tihany, in the Biological Research Institute of the Hungarian Academy of Sci­ ences, coinciding with the 40 years anniversary of this Institute. Its Department of Experimental Zoology, representing the most important basis for researches in Hungary on the nervous system of invertebrates, organized the meeting. The Symposium covered both morphological and functional aspects of inver­ tebrate neurobiology from the viewpoints of elementary processes as well of regu­ latory mechanisms. The complex approach of identic or similar problems is a generally accepted trend in biological research - this tendency is well reflected in the 34 papers presented by participants of the Symposium coming from different countries of Europe and the United States. The volume contains all but one of the lectures held at the meeting, the paper of A. K. Voskresenskaya included in the Proceedings could not be read because of the tragic death of the author, some weeks before the Symposium. The volume is separated into 4 parts according to the 4 days program, however this division is rather tentative because of over­ lappings in the different fields. Discussion following the lectures are also pub­ lished in short, however it was impossible to give a full picture in this respect. The Biological Department of the Hungarian Academy of Sciences deserves special gratitude for the financial support of the Symposium.