An ethnobotanical investigation on the medicinal uses of some species of Terminalia and Combretum (Combretaceae) was carried out in Mbeya, Tanzania during a 5-weeks field expedition. Of the sixteen species collected, Combretum fragrans F. Hoffm., Combretum molle G. Don., Combretum psidioides Welw., Combretum zeyheri Sond., Terminalia kaiserana F. Hoffm. and Terminalia sericea Burch ex. DC. have medical applications against various bacterial infections, such as gonorrhoea and syphilis, and against symptoms like diarrhoea, hypertension and even cancer. Antimicrobial screening of the crude extracts of the selected Combretum and Terminalia species was performed by the agar diffusion method. Among the most effective extracts were methanol extracts of the roots of Terminalia sambesiaca Engl. & Diels., T. kaiserana Guill. & Perrott., T. sericea Burch. ex DC., C. fragrans F. Hoffm. and Combretum padoides Engl. & Diels., all of which showed marked inhibition against Gram-positive bacteria, and were also good inhibitors of Enterobacter aerogenes. All four of the extracts of the roots of T. sericea tested, (methanol, ethanol, acetone and hot water) had good antimicrobial activity. A methanolic leaf extract of T. kaiserana was the only extract to have a bacteriocidic effect on Escherichia coli. Methanol root extracts of T. sambesiaca and methanol leaf extracts of T. sericea were the most effective against Candida albicans. The results of the antimicrobial screening support the ethnomedical uses of these plants.