A method of manufacturing a low-pressure arc discharge lamp formed by interconnecting two or more adjacent glass discharge tubes. A hermetically sealed common passageway between the two adjacent tubes is formed by positioning the tubes in a contiguous relationship to define at least one common location of contact. Heating a preselected area of the internal surface of each of the tubes relative to the common location of contact to soften the glass to the extent a common passageway is defined between the tubes. Thereafter, separating the tubes a predetermined distance while the glass is in a softened state to stretch the softened glass, thereby extending the common passageway between the tubes. The technique may be applied to multiple tube assemblies precoated with a luminescent layer by alternating the end of the tube at which the passageway is formed. Once the tubes are joined, they may be processed by current manufacturing techniques to produce a low-pressure arc discharge lamp.