Fir dwarf mistletoe (Arceuthobium abietinum, Viscaceae) is a common parasite of California white fir (Abies lowiana) and red fir (Abies magnifica) in California. Based on its host specificity, fir dwarf mistletoe consists of two special forms: A. abietinum formae specialis concoloris on California white fir and A. abietinum f. sp. magnificae on red fir. I sampled 17 populations of each special form in the Sierra Nevada and extreme southern Cascade Mountains (Mt. Lassen area) and completed additional morphological measurements of male and female plants, flowers, and fruits. As reported by previous studies, my results demonstrated that these special forms are morphologically similar. No significant differences were detected between the plant, flower, or fruit dimensions measured. The plant color of white fir and red fir dwarf mistletoe was also similar for both male and female plants, but some plants of red fir dwarf mistletoe are more brown-green than white fir dwarf mistletoe, particularly in the northern end of its geographic range. Based on the results of this study no change in the taxonomic status of the special forms of fir dwarf mistletoe was recommended.