A radar experiment was conducted on August 18, 1978, at Kwajalein Atoll, Marshall Islands, to investigate the spatial relationship of 1-m equatorial spread F irregularities to plasma bubbles (localized depletions in F layer plasma density). East-west scans were made with Altair, an incoherent scatter radar, to spatially map (1) the backscatter produced by field-aligned irregularities and (2) the electron density distribution of the background F layer. Plasma bubbles were spatially mapped for the first time with an incoherent scatter radar. By assuming invariance along the magnetic field lines (over distances of less than 100 km) we show that 1-m field-aligned irregularities are directly related to plasma bubbles.