Acoustic properties of 980 tokens of sibilants /s, z, [approximately]/ produced by 17 Canadian English-speaking female and male tongue cancer patients were studied. The patients had undergone tongue resection and tongue reconstruction with a radial forearm free flap (RFFF). The spectral moments (mean, skewness) and frication duration were analysed in connected speech samples produced before the tongue resection, and 1, 6 and 12 months after the surgery. The effects of radiation therapy (RT) and inclusion of the floor of the mouth (FOM) were also studied. Acoustic changes were observed only on alveolar sibilants /s, z/ such that speech was found to improve towards normal over the 1-year period. The reduction of acoustic distinction between /s, z/ and /esh/ was short term. A history of RT and involvement of the FOM had no differing effects on outcomes compared with non-RT or non-FOM. Variability between individuals was found, accentuating the speaker-specific abilities for adaptation, compensation and relearning after oral reconstruction. (Contains 1 table and 2 figures.)