Fluorescence in the transcriptional dpy-18prom::GFP reporter strain was first detected at the bean stage of embryogenesis in hypodermis and muscle, and gfp continued to be expressed in these tissues, as well as in motor neurons and in other unidentified neurons, during embryonic development. Postembryonically, dpy-18prom::GFP is expressed in a similar pattern and is more expansive than observed previously (Hill et al., 2000). In young larvae, dpy-18prom::gfp is expressed in the hypodermis, in muscle, in a few unidentified neurons in the head and tail, and in motor neurons.