Аннотация:Photoelectric U, B, V and photographic B, V photometry of Aql X-1 during the flare of July-August 1978 is reported. The optical radiation was variable, exhibiting a period matching the 1.3 day X-ray period; the object is therefore a binary system. The interstellar absorption is estimated; if the object is of spectral type B2 V-B3 V its distance would be approximately 10 kpc. The color variations in Aql X-1 are similar to those in the recurrent X-ray nova V616 Mon.