The abundance of cultivable methanotrophs and methanogens, and the potential methanogenic (PMGA) and methanotrophic (PMTA) activities were estimated in 22 rice field soils, These measurements where then related to major soil physico chemical propel-ties. Methanogens ranged from less than 10(1) g(-1) d.w. to about 10(6) g(-1) d.w. on H-2/CO2 and formate, 10(5) g(-1) d.w. on methanol, and 10(4) g(-1) d.w. on acetate. Methanotrophs ranged from 10(3) to 10(7) g(-1) d.w. and were 4-10(4) times more abundant than methanogens in most soils. Average PMGA over six weeks ranged from 0 to 0.14 mol m(-2) d(-1) in control soils and from 0.21 to 0.79 mol m(-2) d(-1) in soils enriched with straw. PMTA ranged from 0 to 1.8 mol m(-2) d(-1) Correlation studies and principal component analysis indicated that (1) methanogenic or methanotrophic abundance in a dry soil did not reflect its potential to produce or oxidize CH4 and that activities were mostly substrate dependent, (2) methanogenesis and methanotrophy were positively correlated in terms of populations but not in terms of activities, (3) PMTA was higher than PMGA in most soils, (4) the PMTA/PMGA ratio was mostly governed by PMTA, and (5) soils prone to methanotrophy were above neutrality, rich in available P and with lower clay content.