Hereford United notched their fourth win on the trot to send them second in League Two and provide a major blow to Chesterfield's own promotion hopes.
Sherjill MacDonald and Gary Hooper were again the Bulls goal heroes and have now scored nine goals between them in a week as United have sent heir own prospects of going up soaring.
Hereford took the lead in the eighth minute from their first clear opening.
MacDonald, who has been in inspired form since joining the Bulls on loan from West Bromwich Albion, scored from close range after Clint Easton had headed on Kris Taylor's cross.
Chesterfield looked a dangerous proposition going forward and could have drawn level on 12 minutes. Steve Fletcher headed the ball down to Alan O'Hare, whose shot flashed just wide of an upright.
Fletcher then sent a header looping narrowly over the bar from Jamie Ward's cross.
There were penalty appeals at both ends which, on another day, might have been given, before Hereford extended their advantage in first-half injury time.
Simon Johnson, who had been a lively attacker throughout the half, was brought down wide on the right and Easton's free-kick was hammered in at the far post by Hooper.
The visitors piled forward at the start of the second half but were rarely able to turn their possession into clear shooting chances.
Kevin Cooper gave Wayne Brown an anxious moment, however, with a 20-yard drive which flashed inches wide.
And the Hereford keeper did well to foil substitute Lloyd Kerry, parrying a powerful drive away for a corner.
But the Bulls, although pressed back for much of the period, maintained their threat and MacDonald almost added a third with a powerful header from an Easton corner which Spireites keeper Michael Jordan beat out from point-blank range.