The record power profile (RPP) has gained popularity as a method of monitoring endurance cycling performance. However, the expected variation of cyclists' performance between seasons remains unknown. We aimed to assess the between-seasons variability of peak performance (assessed through the RPP) in male professional cyclists. The study followed a longitudinal observational design. Sixty-one male professional cyclists (age 26 [5]y) with power output data from both training sessions and competitions were analyzed for a median of 4 consecutive seasons (range 2-12). The highest mean maximum power values attained for different durations (from 10s to 30min), as well as the resulting critical power, were determined for each season. Within-cyclist variability between seasons was assessed, and the upper threshold of expected changes (ie,twice the normal coefficient of variation) was determined. All mean maximum power values showed an overall high agreement and low variability between seasons (intraclass correlation coefficient [ICC]= .76-.88 and coefficient of variation [CV]= 3.2%-5.9%), with the lowest variability observed for long efforts (>1min). Critical power showed an ICC and CV of .79 (95% CI, .70-.85) and 3.3% (95% CI, 3.0%-3.7%), respectively. Upper thresholds of expected variation were <12% for short efforts (≤1min) and <8% for long efforts. "Real-world" peak performance assessed through the RPP shows a low variability between seasons in male professional cyclists-especially for long efforts-with expected variation being around 6% and 3% for short (≤1min) and long efforts, respectively, and with changes >12% and >8%, respectively, being infrequent for these effort durations.