BACKGROUND: Methane (CH 4 ) produced during ruminal fermentation represents a loss of 10-11% of gross energy intake. The use of browse species containing tannin as feed supplement for ruminants tends to increase in order to reduce CH 4 production. The present study was conducted to evaluate some tropical plants containing tannin as feed supplement (200 g kg -1 ) on in vitro CH 4 production and fermentation parameters. RESULTS: The crude protein (CP) content ranged from 87 to 390 g kg -1 dry matter (DM) and was highest in Sesbania grandiflora (L.) Poiret. The neutral detergent fibre (NDF) concentration was highest in Pennisetum purpureum Schumach (725 g kg -1 DM) and lowest in S. grandiflora (330 g kg -1 DM). The ranking order of plants based on their total tannin content was Acacia mangium Willd. > Biophytum petersianum Klotzch > Jatropa curcas Linnaeus > Psidium guajava Linnaeus > Phaleria papuana > Persea americana Mill. > S. grandiflora. Methane gas production after 48 h of incubation was significantly (P < 0.05) lower with inclusion of A. mangium (PP + AM), B. petersianum (PP + BP), J. curcas (PP + JC) or P. guajava (PP + PG) as compared to control feed (PP). There was negative correlation between total tannin content and CH 4 production at 48 h of incubation (r = -0.76). Concentration NH 3 -N was significantly (P < 0.01) higher with inclusion of S. glandiflora. Inclusion of P. guajava significantly (P < 0.05) suppressed protozoa population by 49.7% relative to control feed (PP). CONCLUSION: It was concluded that A. mangium, B. petersianum, J. curcas and P. guajava have potential to be used as a feed supplement to reduce CH 4 production in ruminants.