During the early solidification of cast irons austenite tends to freeze dendritically. This has importance for various casting defects and the development of graphite and the eutectic. While dendrites normally merge with the eutectic austenite and transform into ferrite or pearlite, they leave noticeable traces in the final material. A measure of the dendrite microstructure structure has been shown to affect properties in gray and compacted graphite irons. This presentation reviews selected research work within this topical area.