Dorham reviewed the album in the December 1965 issue of DownBeat, awarding it 4.5 out of 5 stars, but commented: "Emotionally, as a whole, this one is lacking. It's mostly brain music... This type of music has that drone thing that I don't like, but because of the almost flawless presentation, I give five stars—but only four stars for the writing and effort—and no stars for the over-all sound. E.S.P. music in general is monotonous—one long drone." Recent commentators have been more positive overall. Stanley Crouch wrote: "the music still sounds fresh. The trumpeter was in superb form, able to execute quickstep swing at fleet tempi with volatile penetration, to put the weight of his sound on mood pieces, to rear his way up through the blues with a fusion of bittersweet joy and what Martin Williams termed 'communal anguish.' The rhythm section played with a looseness that pivots off Williams's cymbal splashes and unclinched rhythms, Carter walking some of the most impressive bass lines of the day, and Hancock developing his own version of the impressionism that Evans was making popular." Davis biographer John Szwed wrote: "The mixture of the abstract and the earthy that Davis had so often seemed to be reaching for began to take shape with this record. Wayne Shorter's ease with indeterminate melodies and his eagerness to join the rhythm section in churning up the music to the point that it threatened to break loose from the traditions of jazz gave Davis the space he needed to reexamine his own playing." In a review for AllMusic, Stephen Thomas Erlewine commented: "ESP marks the beginning of a revitalization for Miles Davis, as his second classic quintet... gels, establishing what would become their signature adventurous hard bop. Miles had been moving toward this direction in the two years preceding the release of ESP and he had recorded with everyone outside of Shorter prior to this record, but his addition galvanizes the group, pushing them toward music that was recognizably bop but as adventurous as jazz's avant-garde. Outwardly, this music doesn't take as many risks as Coltrane or Ornette Coleman's recordings of the mid-'60s, but by borrowing some of the same theories -- a de-emphasis of composition in favor of sheer improvisation, elastic definitions of tonality -- they created a unique sound that came to define the very sound of modern jazz... The compositions are brilliantly structured as