| N6022, [benzamido ring-14C(U)]- | MC 2769 |
| N-[3,5-bis(trifluoromethyl)phenyl]-2-hydroxy-3-[3H]-5-(trifluoromethyl)-benzamide, [3H]- | MT 2159 |
| Naphthalene, [1,4,5,8-14C]- | MC 2147 |
| Naphthaleneacetamide, [1,4,5,8-14C1]- | MC 2602 |
| 1-Naphthoic acid, [D7]- | MD 103 |
| Nelfinavir, mesylate | M 1824 |
| Neomycin B, sulphate, [3H]- | MT 1756 |
| Nepafenac, [aniline-14C(U)]- | MC 2263 |
| Niacin mononucleotide, [carboxyl-14C]- | MC 1388 |
| Niacin riboside, [carboxyl-14C]- | MC 2048 |
| Nicotinamide, [carbonyl-14C]- | MC 1427 |
| Nicotinamide, [6-3H(N)]- | MT 1937 |
| β-Nicotinamide mononucleotide, [4-3H(N)]- | MT 516 |
| Nicotinamide adenine dinucleotide, [adenine-2,8-3H]- Discontinued | MT 865 |
| Nicotinamide adenine dinucleotide, [3H]- | MT 2042 |
| β-Nicotinamide ribose,monophosphate, [4-3H(N)]- | MT 516 |
| D,L-Nicotine, hydrochloride salt, [pyrrolidine-2-14C]- | MC 484 |
| Nicotine hydrochloride, [pyridyl-5-3H]- | MT 1978 |
| Nicotinic acid, [carboxyl-14C]- | MC 1324 |
| Nicotinic acid, [pyridyl-2-14C]- | MC 1168 |
| Nifedipine, [dihydropyridine-4-14C]- | MC 2448 |
| Nifurtimox, [3-methylthiomorpholine dioxide ring 5,6-14C]- | MC 2634 |
| Nifurtimox, [3H]- | MT 1877 |
| Nilotinib, [3H]- | MT 1957 |
| Nipecotic acid, [3H]- | MT 1723 |
| 2'-Nitroacetanilide, [14C(U)]- | MC 2253 |
| 4'-Nitroacetanilide, [13C6]- | MG 122 |
| 4'-Nitroacetanilide, [14C(U)]- | MC 2054 |
| o-Nitroaniline, [14C(U)]- | MC 1326 |
| o-Nitroaniline, [3,5-3H]- | MT 1772 |
| p-Nitroaniline, [14C(U)]- | MC 1327 |
| Nitrobenzene, [14C(U)]- | MC 254 |
| 2-Nitrobenzoic acid, [carboxy-14C]- | MC 2367 |
| 3-Nitrobenzoic acid, [carboxy-14C]- | MC 2368 |
| S-(p-Nitrobenzyl)-6-thioinosine, [3H]- | MT 682 |
| S-(p-Nitrobenzyl)-6-thioinosine, [3H]- | MT 682L |
| 2-Nitro-1H-imidazole, [2-14C]- | MC 498 |
| 4-Nitroiodobenzene, [2-14C]- | MC 2228 |
| 2-Nitromethylbenzoate, [carboxy-14C]- | MC 2391 |
| o-Nitromethylbenzoate, [ring-14C(U)]- | MC 2229 |
| 1-Nitronaphthalene, [1,4,5,8-14C]- | MC 2195 |
| 4-Nitrophenylacetic acid, [carboxy-14C]- | MC 2393 |
| 2-Nitrophenylacetonitrile, [nitrile-14C]- | MC 2404 |
| 1-Nitropropane, [1-14C]- | MC 2286 |
| 2-Nitropropane, [2-14C]- | MC 2282 |
| 5-(2-Nitropropenyl)-benzo[1,3]dioxole, [phenyl-14C(U)]- | MC 2277 |
| Nitrosodimethylamine, [methyl-14C]- Discontinued | MC 1332 |
| N'-Nitrosonornicotine, [pyridyl-5-3H]- | MT 1622 |
| (R)-N'-Nitrosonornicotine, [pyridyl-5-3H]- | MT 1679 |
| (S)-N'-Nitrosonornicotine, [pyridyl-5-3H]- | MT 1678 |
| 6-Nitro-1,2,3,4-tetrahydroisoquinolinyl-t-butylcarbonate, [14C]- | MC 2256 |
| 2-Nitrotoluene, [ring-14C(U)]- | MC 2425 |
| 3-Nitro-L-tyrosine, [3H]- Discontinued | MT 1712 |
| (R)-NNAL, [5-3H]- | MT 1981 |
| (S)-NNAL, [5-3H]- | MT 1773 |
| NNK, [pyridyl-5-3H]- (4-(Methylnitrosamine)-1-(3-pyridyl)-1-butanone, [pyridyl-5-3H]-) | MT 1621 |
| NNN, [pyridyl-5-3H]- (N'-Nitrosonornicotine, [pyridyl-5-3H]-) | MT 1622 |
| Nonanoic acid, [carboxyl-14C]- | MC 1333 |
| Nonanoic acid, [9-3H]- | MT 1787 |
| Norastemizole, [2-14C]- | MC 2024 |
| D-Norleucine, [1-14C]- | MC 1423 |
| L-Norleucine, [1-14C]- | MC 1424 |
| Novantrone | |
| NSC 617145, [1-14C]- | MC 2722 |