The aims . of this research were twofold, firstly to find out if interferential currents could reduce the healing time for fractures of the tibia and thereby prevent nonunion and secondly to develop a model which could predict nonunion, given the subject characteristics such as race, mechanism of injury, severity of fracture etc. Subjects, males only between the ages of 12 and 86, who had sustained fractures of the tibiae were entered into this double blind clinical trial on admission to the orthopaedic wards at Groote Schuur Hospital (between January 1989 and October 1991). According to strict inclusion and exclusion criteria, a final sample of 227 cases (208 subjects) were entered by block randomisation into three groups; an experimental group (n=41), placebo group (n=35) and control group (n= 151). lnterferential currents were applied to the experimental group via suction electrodes for, 30 minutes per day for 10 days, using a beat frequency of 10 - 25 Hz and a swing mode of 6 ϟ 6. The placebo group had the suction electrodes applied which produce a rhythmical massage effect. Subjects commented on pain relief which resulted in the addition of the control group as a check on the possible effect of suction, the control group received no intervention. The data were analysed firstly, by using the ANOV A with continuous covariates which resulted in a finding of no significant difference in the time taken to union for the three groups. The second statistical analysis using the same data set, were logistic regression models demonstrating risk factors for nonunion within 24, 32 and 40 weeks. These models were then validated, showing sensitivity and specificity for a variety of possible cutoffs. The conclusions reached about the validity of these models were that they could not be used to predict, accurately enough, those cases where surgical intervention would be necessary; however, for low cost non-invasive intervention they may have value.