There are many prosthetic feet (Pfeet) on the market, and those in the same category do not necessarily have the same properties. We assessed three different Pfeet in terms of gait patterns on various terrains, balance and walking speed in a randomized double-blind controlled single-subject multiple-rater clinical trial. The patient was a 43-year old man who was an active prosthesis user and was amputated at transtibial level because of injury 17 years ago. One Solid Ankle Cushion Heel and two Dynamic Elastic Response (DER) Pfeet were tried six times in random order. The patient walked on flat, uneven, sloped terrain and stairs. Gait pattern was rated in comparison with the patient's previous prosthetic foot (Pfoot) by a physiatrist, physiotherapist, prosthetist and the patient; one-leg standing test on the prosthesis and 10-m walking test were also performed. The ratings differed significantly between the raters on each terrain, and there was no agreement among the raters regarding the ranking order of the Pfeet. All the Pfeet were generally rated as worse than the patient's previous one. The patient gave lower ratings on average than the professionals and recognized the order of the tested Pfeet. The results of one-leg standing test with one DER and the Solid Ankle Cushion Heel Pfoot were statistically significant better than with the other DER and the patient's previous Pfoot. Our study therefore indicates that rehabilitation professionals, when blinded, cannot always reliably observe differences in walking on different terrains with different Pfeet. The patient may feel the differences, but those may not match what the manufacturers declare.