One of the legal tasks of the Coordinating Laboratories for the Surveillance of Radioactivity in the Environment is to carry out quality assurance measures, including interlaboratory comparisons. The Coordinating Laboratory of the Max Rubner-Institut in Kiel, Germany, is responsible for the environmental media soil, vegetation, animal feed and foodstuffs of plant and animal origin. Spinach was selected for this interlaboratory comparison, because it is mentioned as an example of the “representative” medium “leafy vegetables” and thus for all food crops in the official German surveillance program in the event of a nuclear incident.¹ However, with fresh spinach a homogeneous distribution of added nuclides is hardly achievable. Therefore finely milled spinach powder was chosen as a matrix in this interlaboratory comparison. The participants had to determine the specific activities of the naturally present K-40 and added nuclides I-131, Cs-134, Cs-137 and Sr-90. For the dry matter determination a fast method was stipulated.