The effect of ontogenetic increases in total length on burst swimming performance was investigated in tadpoles of the striped marsh frog (Limnodynastes peronii) over the total‐length range of 1.5–4 cm and Gosner developmental stages 25–38. The burst swimming performance of tadpoles at 10° and 24°C was determined by videotaping startle responses with a high‐speed video camera at 200 Hz and analysing the sequences frame by frame. Maximum swimming velocity ( ) and acceleration ( ) increased with total length (L) at a rate that was proportionally greater than the increase in total length (i.e., positive allometry; exponents >1) and was described by the allometric equations and at 10°C and and at 24°C. Stride length increased with a total‐length exponent of approximately 1 but was unaffected by temperature. Tail‐beat frequency was not affected by total length and increased from Hz at 10°C to Hz at 24°C. Developmental stage did not significantly influence the relationship between total length and or . Furthermore, temperature and the associated changes in water viscosity did not affect the relationship between total length and burst swimming performance. At their , Reynolds numbers ranged from approximately 1,500 in the smaller tadpoles up to 50,000 for the larger animals at 24°C. We suggest the positive allometry of in larval L. peronii was due in part to the increases in tail width (TW) with total length ( L^1.66), possibly reflecting the increasing importance of burst swimming performance to survival during larval development.