This is an announcement for the paper "Extensions by spaces of continuous functions" by Jesus M. F. Castillo and Yolanda Moreno. Abstract: We characterize the Banach spaces X such that Ext(X, C(K))=0 for every compact space. Archive classification: Functional Analysis Mathematics Subject Classification: 46B03; 46B07 Remarks: 9 pages The source file(s), ECK.tex: 28947 bytes, is(are) stored in gzipped form as 0410256.gz with size 10kb. The corresponding postcript file has gzipped size 48kb. Submitted from: castillo@unex.es The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/math.FA/0410256 or http://arXiv.org/abs/math.FA/0410256 or by email in unzipped form by transmitting an empty message with subject line uget 0410256 or in gzipped form by using subject line get 0410256 to: math@arXiv.org.