We report the detection in x ray of a high redshift (z = 4.30) radio-loud quasar, GB 1508+5714, the first radio-selected z > 4 quasar seen in x- rays. The quasar was observed serendipitously with the Einstein observatory IPC at 0.02 +/- 0.003 counts s^-1^. It is ten times brighter than the other two z > 4 x-ray detected quasars. The x-ray source is unusually hard, implying either α_E_ < -0.2, or N_H_> 10^22^ atoms cm^-2^ (1σ limits) for a simple power-law plus intrinsic (z = 4.3) absorption. Intrinsic absorption would make GB 1508+5714 similar to a large fraction of z ~ 3 radio-loud quasars.
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Mathur et al. (1995) studied this question.