AbstractPurpose. To investigate whether there was a difference in hamstring length between patients with patellofemoral pain syndrome and healthy asymptomatic control participants between 18 and 35 years old. Relevance. Short hamstrings may produce greater patellofemoral joint reaction forces. Only three studies, which had conflicting results, have measured the hamstring length in this patient group (Smith et al., 1991; Witvrouw et al., 2000; Piva et al., 2005). Subjects. Two groups were tested, one was diagnosed with patellofemoral pain syndrome (mean age 27 years, n = 11, six males, five females) and one was of asymptomatic control participants (mean age 25 years, n = 25, 13 males, 12 females). Methods. Ethical approval was granted by the Local Research Ethics Committee and a cross‐sectional observational study was carried out in a hospital's physiotherapy department. Hamstring length was evaluated using the passive knee extension method and a masked universal goniometer to measure the popliteal angle. Analysis. An independent t‐test was used to evaluate between‐group differences. Results. Mean (standard deviation) values for hamstring length were 145.6 (8.7)° for the patellofemoral pain patients and 153.7 (10.1)° for the asymptomatic control participants. The mean (95% confidence interval) difference between the groups was 8.0 (0.8 to 15.1)°, and this was statistically significant (p < 0.05). Discussion. Although limited by a small sample size, these results show that hamstring length is shorter in the patellofemoral patient group than in the asymptomatic participants. It is unclear whether this is a cause or an effect of the condition. Further research should study how hamstring length changes with rehabilitation and its relationships with pain. Copyright © 2008 John Wiley & Sons, Ltd.