The trial court properly held that Owen’s agreement not to solicit former customers was enforceable under B&P Code 16601 since Owen had sold all of his interests in several affiliated businesses to Blue Mountain as the first step in forming a joint venture with a Chinese company. Even though Owen regained a 50% ultimate beneficial interest in Blue Mountain once the joint venture was formed, the prior sale of all his interest in the affiliated businesses to Blue Mountain was enough to make section 16601 applicable. Also, it didn’t matter that the non-competition clause appeared in an employment agreement executed as part of the same transaction rather than in the agreement for sale of the businesses. Owen’s letter directed solely to his former customers and employees went beyond simply stating he had formed a new business and constituted a solicitation violating his non-competition agreement.