To determine more detailed locations of human P/Q-type (alpha 1A), N-type (alpha 1B), and R-type (alpha 1E) calcium channel genes, we have mapped CACNL1A4 (alpha 1A), CACNL1A5 (alpha 1B), and CACNL1A6 (alpha 1E) loci using a radiation hybrid panel. Locations of these loci are as follows: WI-4669-5.1 cR3000-CACNL1A4-4.1 cR3000-CHLC.GATA27C12 on chromosome 19; D9S158-2.0 cR3000-CACNL1A5-4.3 cR3000-WI-14048 on chromosome 9; D1S215-4.4 cR3000-CACNL1A6-4.5 cR3000-D1S240 on chromosome 1.