This study describes the changes in selected points of the speed curve, stroke rate (SR), and stroke length (SL) of an elite butterfly swimmer and examines their relationship with average speed (AS) and competitive performance. Over eight years, a male swimmer (50 and 100 m: 22.70 and 51.47 s) underwent 18 tests to assess AS, SR, SL, intracyclic speed variation (ISV), and eight selected points of the speed curve. Peak<inf>1</inf> is the maximum speed in the upward kick executed during the arm recovery; peak<inf>2</inf> is the maximum speed in the first downward kick after the arm entered into the water; peak<inf>3</inf> is the maximum speed during the arm pull; and peak<inf>4</inf> is the maximum speed during the arm push combined with the second downward kick. Min<inf>1</inf>, min<inf>2</inf>, min<inf>3</inf>, min<inf>4</inf> corresponds to the minimum speeds found respectively before each peak speed. Official competitive results in 50 (50BF) and 100 m (100BF) within three weeks of the speed tests were registered. SR (r=0.736), ISV (r=-0.493), peak<inf>1</inf> (r=0.555), min<inf>2</inf> (r=0.558), and min<inf>3</inf> (r=0.539) were correlated with AS. 50BF was correlated with AS (r=-0.658) and peak<inf>1</inf> (r=-0.820), whereas 100BF with AS (r=-0.676), SR (r=-0.571), peak<inf>1</inf> (r=-0.758), and peak<inf>2</inf> (r=-0.594). AS increased by improving SR, peak<inf>1</inf> and peak<inf>3</inf>. Increases in min<inf>2</inf> and min<inf>3</inf> indicate better transitions from resistive to propulsive phases. Selected points of the speed curve may predict butterfly performance.