AbstractIn fresh whole plant tissue thiocyanate was not in a “free” state and to obtain satisfactory thiocyanate values it was necessary to disrupt the tissue thoroughly by homogenisation to permit hydrolysis of the thiocyanate‐containing substance.Rape kale contained about 15 mg thiocyanate/100 g of fresh material, less than half the amounts found in thousand head, marrow stem, Maris Kestrel or Canson: there were no consistent differences among the thiocyanate contents of these four types of kale.The thiocyanate content, although fairly constant during most of the growing season, increased about twofold in late September and October then returned to former values. This increase did not occur in rape kale.Small young kale leaves contained more than five times the amount of thiocyanate found in large, fully formed leaves, and about twice the amount present in leaves of intermediate size.