Mature and developing cottonwood (Populusdeltoides Bartr.) and bean (Phaseolusvulgaris L.) leaves were photosynthetically labeled for 30 min with 14CO2. Radioactive compounds in exudate obtained by placing the cut petioles in 20 mM Na2EDTA for 6 h were compared with those found in chloroform–methanol–water extracts of leaf lamina and petiole. Of the total activity lost in 6 h, 54% was recovered in the exudate from mature bean leaves compared with 3% recovered from cottonwood leaves. Smaller amounts were recovered in exudate from developing leaves compared with mature leaves of both species. Thus EDTA was not very effective for maintaining translocation rates in excised cottonwood leaves. Most of the radioactivity in the exudate was in sugars, indicating relatively pure sieve tube contents. However, radioactive amino acids and organic acids were always present, particularly in exudate from developing leaves. These amino and organic acids could either be derived from metabolism outside of the phloem with subsequent leakage into the EDTA solution, or be a component of the normal translocation stream. Of the total activity in exudates from developing cottonwood leaves, 17% was found in the amino acid and 33% was found in the organic acid fraction compared with 7% and 5% in these fractions, respectively, from developing bean leaves. The distribution of activity in the sugar, amino acid, and organic acid fractions of cottonwood petiole extract was similar to that found in the exudate. In contrast, proportionally less sugar and more amino acids and organic acids were labeled in bean petiole extract compared with the exudate, indicating lateral movement and metabolism in the bean petiole.