Glucose-6-phosphate dehydrogenase (G6PD) activity, lactate dehydrogenase (LD) activity, and cytometric flow measurement of nuclear size and cell cycle distributions were registered in biopsy specimens from adenomas and hyperplastic polyps less than 5 mm. The G6PD and LD activities in adenomas, 36.8 +/- 4 U/g protein and 1580 +/- 163 U/g, respectively, were significantly higher than in hyperplastic polyps, 17.9 +/- 2.6 U/g and 1080 +/- 107 U/g, or in normal mucosa, 14.7 +/- 0.8 U/g and 1174 +/- 56 U/g, respectively. G6PD activity was significantly higher in adenomas with moderate (44 +/- 5.8 U/g) than in those with mild (32 +/- 5.9 U/g) dysplasia, in contrast to LD. No difference in enzyme activity was observed between hyperplastic polyps and normal mucosa. The growth of adenomas and hyperplastic polyps was not significantly different during the 2 years of follow-up study before biopsy specimens were taken. Increased nuclear size, unrelated to grade of dysplasia, was registered in 12 of 20 adenomas, in 1 of 10 hyperplastic polyps, and in 2 of 42 specimens from normal mucosa. Adenomas and normal mucosa from individuals with adenomas showed a significantly increased number of cells in S-phase. The values were 10.2 +/- 3% and 8.8 +/- 4%, respectively. Normal control value was 6.8 +/- 2.2%. An increased number of cells in G2-phase was observed only in adenomas (6.9 +/- 2.7% compared with 4.9 +/- 1% in controls). None of the adenomas showed aneuploidy.(ABSTRACT TRUNCATED AT 250 WORDS)