Uganda National Examination Board, has withheld results of 279 (27%) candidates due to external assistance.
UNEB executive secretary Mathew Bukenya said the most affected subjects were mathematics and Arts.
12 of the 103 special needs candidates that registered for exams were blind.
31.3% candidates offered Maths, 16.9% Physics, 12.1% Chemistry and 13.0% Biology.
A total of 101,268 candidates registered for UACE 2015 from 2,003 centres compared to 108,419 in 2014.