Abstract: Apparatus for assembling and installing Luer fittings comprises a hand held tool and an associated jig. The main body of the tool comprises an elongated, generally cylindrical housing externally configured to define a comfortable hand grip. An integral, reduced diameter nozzle projects forwardly from the housing for selectively, slidably engaging the male portion of a desired Luer fitting to be assembled. The housing concentrically mounts a spring-biased plunger driven by an external button adapted to be contacted by the user's hand. A metallic drive pin emanating from the plunger drive shaft penetrates the housing nozzle. An internal snap ring seated within an internal housing ring groove limits longitudinal plunger motion. The apparatus also includes an associated jig adapted to be mounted upon a supporting work surface. The jig firmly retains the locking ring of a Luer fitting in proper position for assembly.