This study aimed to isolate mycoplasmas from oral cavity of patients with oro-dental diseases, to evaluate their role in pathogenesis of these diseases, and to evaluate the effects of some antibiotics on them. The population enrolled in this study was individuals attending the dental outpatient clinics in the dental specialty center in Basrah, from private dental clinic, and from otolaryngology outpatient clinic. It consisted of 154 patients with periodontal diseases (gingival diseases & periodontal abscesses) and oral ulcers of different types, in addition to that, 50 healthy subjects were included as control group. It included 112 males and 92 females, their age ranged from 6 to 68 years. This study extended from the period between August 2010 to December 2011. Samples from gingival sulcus or periodontal spaces were obtained by using paper points and swabs from ulcer surface, all specimens were cultured within one hours of sampling. For the isolation of mycoplasma, each specimen was directly inoculated into the liquid phase of MDCS. Mycoplasma spp. were isolated from 120 individuals out of 204 enrolled in this study, males affected more than females, the commonly affected age group was 20-29 years. Smoking play a clear role in causation of dental diseases and mycoplasma found more in smoker patients, (62 were smokers, 36 were non-smokers).Gingival diseases were commonly presented (62 patients), followed by inflammatory oral ulcers (45 patients). Mycoplasma salivarium was the frequently isolated species (70.8%), followed by mycoplasma orale (isolated from 16.6%). Single mycoplasma infection was found in 4 cases, 3 in gingival diseases which were 2 mycoplasma salivarium and one M.orale. The last spp. was M. pneumoniae, it was isolated from periodontal abscess. Tertracycline and erythromycin showed good inhibitory effects against mycoplasmas. In conclusion, Mycoplasma isolated from males with oro dental diseases more than females. The mostly affected age group was 20-29 years of age. Mycoplasma salivarium was the commonest isolated species, followed by mycoplasma orale. It is rare to find single mycoplasma infection in the oral cavity, just 4 cases were documented from total 98 patients. Tetracycline and erythromycin can significantly inhibit the growth of mycoplasma.