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The status of our on-going survey of the fields of BL Lac objects is presented. Observations were obtained in January 1994 at the ESO NTT under excellent conditions. Evidence is mounting that BL Lacs are found in moderately rich clusters (Abell richness class 0-1), with some individual objects in richer clusters (Abell richness class 2). The results for our new sample of BL Lacs are compared to preliminary results from our study of F-R I galaxy environments. Many BL Lacs are also found with nearby companions, which may be interacting with the BL Lac host. Such interactions may cause the nuclear activity. In addition, an intercluster medium or material left over from interaction may produce the X-ray absorption features found in several BL Lacs.
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