The aim of this study was to investigate the presence of different mycoplasmal species in blood samples from patients with chronic fatigue syndrome and/or fibromyalgia syndrome. Previously, more than 60% of patients with chronic fatigue syndrome/fibromyalgia syndrome were found to have mycoplasmal blood infections, such as Mycoplasma fermentans infection. In this study, patients with chronic fatigue syndrome/fibromyalgia syndrome were examined for multiple mycoplasmal infections in their blood. A total of 91 patients diagnosed with chronic fatigue syndrome/fibromyalgia syndrome and with a positive test for any mycoplasmal infection were investigated for the presence of Mycoplasma fermentans, Mycoplasma pneumoniae, Mycoplasma hominis and Mycoplasma penetrans in blood using forensic polymerase chain reaction. Among these mycoplasma-positive patients, infections were detected with Mycoplasma pneumoniae (54/91), Mycoplasma fermentans (44/91), Mycoplasma hominis (28/91) and Mycoplasma penetrans (18/91). Multiple mycoplasmal infections were found in 48 of 91 patients, with double infections being detected in 30.8% and triple infections in 22%, but only when one of the species was Mycoplasma pneumoniae or Mycoplasma fermentans. Patients infected with more than one mycoplasmal species generally had a longer history of illness, suggesting that they may have contracted additional mycoplasmal infections with time.